i got 20 calculation questions in my exam and 18 of those attempts were correct..and for each of my correct answer i give you the credit coz i followed all your vids before my exam and practised..I freaked out before but as i began to practise from your vids...it made me very easy to understand..all i can do is pray for u from my heart that you are doing such a great job and a big thankyou!!! and my advice to fellow test takers is that dont freak out like i was very worried before...just practise out from this channal and i swear ull feel a lot of confidence building in you ...his way of explaining is excellent so just his vids are enough for you to learn thoroughly..! ALL THE BEST :)
This is fantastic; I appreciate the actual explanation of the technique being used (e.g. dimensional analysis) instead of just steam rolling through the problem.
Thank you!, Thank god i found your Videos, the way you calculate is just amazing and simple, cant believe i was trying to memorize all those formulas when i can do this instead. Props to you doctor!
Sure thing! I just took the ptce and passed!!. I would have been doomed if i had not learned your method, over 25% was math problems i could solve this way.
Yayyy I got 5.1 when I first worked it out! I still watched the rest of the video and it was very well explained; I will definitely use this method to solve more complicated problems though. Thank you!
Hi Ana, I will do this when I get home later. Basically, you have to calculate the total weight of the active ingredient from both ointments and the total weight of the final product, then change that to a percentage.
Hi Jeffrey. The three problems you asked about are all solved the same way. Each problem has three parts to it: 1) A given, the units of the answer, and one or more ratios. In each problem start by writing down the given ( 0.075mg/day for the first problem, 8 oz for the second problem, 10 mL for the third problem) and the units of the answer for each: mg/h, days, days. For problem 1) 0.075mg/d = mg/h, you can see that you only have to change days to hours. You will do that with the conversion factor 1 day/24 h. (0.075 mg/d)(1 day/24 h) = 0.003125 mg h. Of course you could just write it as 0.075 mg/24 h and divide it out. Problem 2) 8 oz = days. On these problems, I usually tell my students to calculate how much per day so you can cut down on the number of ratios in the problem. 8 oz (1 day/8 tsp)(6 tsp/ 1 oz) = 6 days. See how all of the unwanted units cancel out? Problem 3) 10 mL = days. The ratios you will need are 100 units/mL and 1 day/60 units. 10 mL(100 units/mL)(1 day/60 units) = 16.7 days. It doesn't matter that 2 vials are dispensed because they are asking how long 10 ml will last. This method may seem a little harder than other methods at first, but once you learn it you will be able to do most all problems that do not involve mixing or dilutions. Sometimes it is kind of hard to determine what the given is in the problem, but with a little practice you will learn to recognize it. Let me know if you have any other questions.
+Brad Wojcik I figured out when I should times or divide based on the Kg,G,Mc,Mcg scale. Pretty cool. I just hope that I pass this test. I am studying 200 prescriptions: the Generic Name- Brand Name- Purpose- and their DEA schedule type. I know that I need to know the laws.... Medical Acts... I probably just need to borrow the "Orange Book" from a pharmacy.. Pharmacy Laws... Common Abbreviation.... Codes.. All of this information I need to remember
Thank you so much, you really explained how to break down the problem, I also like the dimensional analysis method as it shows the full problem and allows you to check for any errors, as I'm studying for my PTCB exam, your videos have been very helpful!
Hi Courtney, Thank you for the nice comment. You should learn both dimensional analysis and ratio proportion, but you should also know that chemists, physicists and engineers all use the dimensional analysis method of solving their problems. For some reason, the medical community and pharmacy community use the ratio proportion method. Be confident that if you use dimensional analysis, you are using the safest and most powerful method. I will probably get a nasty comment for this, but I don't care. Dr. Brad
Hi Celina. I think the first way, dimensional analysis, is easier also. Chemists, physicists, engineers all use this method because it is easier and more powerful. For some reason the medical and pharmacy community use the ratio proportion method. You should learn both.
Dear Dr. Brad, i sent you a message just now regarding confusion on setting up a particular dimensional analysis set up. I would love it if you would create a video that covered this simple (yet confusing to me in this moment) problem to show WHICH pieces to fit in the puzzle are needed and which are not. thank you!!
I decided to be a Pharmacy technician as my career and this is my first semester on learning all these new calculations. and these videos def help me. But right now its all sorta confusing especially remembering how many liter or milliliter in an ounce for example
Hello! your videos are easy to follow bc the way you explain things. Im taking my exam this week and trying to brush up on IV calculations. Im trying to memorize these formulas but i don't understand when to use which. The book im using has infusion rate AofF times gtt/ml over Hrs to Admin times 60min/hr. Theres frequency schedule total vol infused over IV rate and IV rate vol infused over infusion time and drip rate vol infused over infusion time multiplied by drip set factor. sorry my msg is long im just really confused 😕 I understand when theyre doing the calculations but some seem similar so I don't know when to use what and why.
You can download my book, Pharmacy Calculations for Pharmacy Technicians: Solving Pharmacy Calculation Problems Without All the Silly Formulas, for free at payhip.com/b/5xVY. It goes into more detail than possible on the videos and is full of practice problems and answers.
I didn't see "divide into 4 doses" and when I got 20.5 mL I though it was wrong, but that is the daily does. I also rounded to the nearest unit when figuring the Pt's weight in kg. which got me 82 kg. rather than 81.8 kg. Should you round to the nearest tenth when doing the PTCB exam? The proportion method has always been a favorite of mine to use in the pharmacy but the dimensional analysis method was also great to learn. Thanks for your videos!
Can you tell me how much morphine would a person be taking daily or every five hours if their drug test says 3000 ml . Every time my doc test me see freaks out and I know I'm taking my meds as prescribed. I have to keep them on schedule or I get a bad headache. This meaning I don't take more than what's prescribed. I never ever double up, if anything I can go without the rneds for several hours past my dosing time but like I said if I do that I get a headache so I keep them as close to the prescribed time frame as possible. I'm starting to wonder if the drug is showing up in high doses due to other possible reasons like maybe my liver isn't precessing the drug properly or maybe I'm not drinking enough water or fluids and it's building up in my system. I'm a chronic pain patient and take it for all over pain , spinal pain fibromyalgia head and neck, hip pain. I hurt all over but every time she test me she tries to take away my meds I've even cut back in order to make sure I have a couple of days on hand in case she's out of the office when my refills are due or sometimes the pharmacy doesn't have the meds in stock in order to fill my script and I'll have to wait. I've never taken more than I'm supposed to. I don't do street drugs either . Never been to jail never want to go so I always use my medication as prescribed, my dog can call me any time and I'll have my meds. I can't for the life of me figure out why she keeps trying to cut my meds back or take me off them when I hurt so bad. I've been in 2 car wrecks neither my fault, one a teenager hit me head on after changing her mind in an intersection she decided not to turn left and jumped back into the oncoming Lane and hit me head on said she was sorry she was speeding and late to a job interview. Because I'm so short the seat belt wraps around my neck really did a number on me. The other an elderly lady hit me head on while she was driving in the wrong lane through a construction area, her kids apologized said they needed to take her license away. I was later hit on top of the head with a Ford aerostar hatch, it hit me so hard it knock me to my knees and blacked out. I've been hit behind twice by you teenagers while I was just sitting at stop lights. And I had a bad overuse injury at a job that I received a settlement for. I live in severe neck & spinel pain everyday all day it never goes away. I need your help trying to figure out what's going on. The only thing I can come up with is maybe the meds are building up in my system . I think it said I had 3000 ml so what would that calculation be in mg tablets per day? Sorry so long winded but I may need to show this to my doctor. I'm hoping to figure out what's going on and why. Thank you kindly
I wish in these videos when your doing the math on the calculator that you would have put it on the board, I’m very new at this and it would help me I did however I did go back and watch the video twice it’s the nice thing about video learning , my question is now it’s 2017 how long are videos going to be good for on TH-cam for pharmacy technician knowledge some I’ve watched are older ones are any too old to be watching ? Or has the ways of doing these calculations not changed in over 10 years ?
Thank you Dr. Brad, I've being practicing with powder volume and I think I got it. but suddenly there is another problem and I got confuse again. This is not powder because I need 3 values and there is not my 3 values. and its not an allegation problem HOW MANY MILLITERS OF A 3% (W/V) WILL BE NECESSARY TO MAKE 6OZ OF A 1:200 SOLUTION? A. 30 ML B. 180 ML C. 25 ML
Hi Ana. First off you to know how to change the 3% w/v and 1:200 into ratios which contain g and mL. 3% w/v is 3 g/100 mL and 1:200 is 1 g/200 mL. If you don't know how to do that, I can send you some info. Just email me at brad.wojcik@gmail.com. First step in the problem is to calculate how many g you will need to make the 6 oz of 1:200 solution. You have to change 6 oz into g using ratios as tools. 6 oz (30 mL/oz)(1 g/200 mL)= 0.9 g. Now calculate how many mL of the 3% solution you need to get the 0.9 g. Here you will change g into mL. 0.9g (100 mL/3 g) = 30 mL You could also use V1C1=V2C2 by changing 1:200 into 0.5% v1(3%)=180 mL(0.5%) Solving for V1 you will get 30 mL. Hope this helps. -Brad
Thank you Dr.Brad again. But instead of multiply 6 oz times 30 I was counting as 600 ml, that's why I could not do it. and V1C1=V2C2 was my first option and off course the answer was wrong. I apologize again.
Hi Ana. For some reason, I couldn’t find you question on the comments, so I am replying here. The question was if you mix 60 g of a 1% ointment is mixed with 80 g of a 2.5% ointment, what is the % of ointment in the final mixture. You have to calculate the total grams of the active ingredient in both ointments and the final weight of the two ointments after they are mixed, then change that back to a percentage. 60 g oint (1 g active ing/100 g oint) = 0.6 g 80 g oint (2.5 g active ing/100 g oint) = 2.0 g. You have 2.6 g active ing in 140 g of oint. 2.6 g a.i. /140 g oint (100%) = 1.86% Also, it is easier if you just email me at brad.wojcik@gmail.com
+Elaine Jones Hi Elaine. I think it would be much more difficult taking it online as you would not have any hands on experience working with IV products, etc.
Hi, I am very curious as to why pharm. techs are doing calculations and not the pharmacist? I would think it would be dangerous for a pharm. tech to do this and not the person with the PhD. Thanks for your reply.
Well I’m new at this pharmacy technician college education and I feel that the pharmacists have enough to do so we do what they use to do and it’s great for us we do a lot of the work for them but they did it all to at some point in time it seems because here he is teaching us...
Here in Hungary the pharmacist does the calculations, the technicians job is to take phine calls, organize medication in alphabetical order and by order of expiration date bring the prescriptions to the pharmacist who will make it and also to take in the orders for medications in the morning. More experienced technicians (after 3 years of work) are allowed to expedite and to help with packaging the medication that te pharmacist makes and also they can help the pharmacist under the pharmacist supervision in dosing medication
I know just as much to the regular joe as a pharm tech but the process is the pharm tech does the calcs and then the pharm d checks the calc and then the pharm tech takes the corections or calcs and performs the grunt work for the sig it a simple mechanic of process called "better than a computer taking all the work out of it instead a less payed person ".
Hi Mr.Brad. Could you please help with this problem? What volume of a 1 in 400 v/v solution is needed to produce 5L of a 1 in 2000 v/v solution? I am not able to do that from the first method?
You can do it a couple of ways. First calculate number of grams in 5 L of the 1:2000 solution then calculate the volume of the 1:400 solution needed to get those grams. 5 L(1 g/2000 mL) (1000 mL/L) =2.5 g. 2.5 g (400 mL/1 g) =1000 mL. You can also use V1 C1 = V2 C2.
question? as we all know in pharmacy we use the metric measuring system. There are several ways how the metric system differs from common household measures. what could be the advantages and disadvantages of each system? and why the metric system is preferred in the pharmacy.
Hi Syeda. The metric system is much easier to use and there is no ambiguity on the units, as there are with household measurements. For example, a teaspoonful can vary depending on how you are measuring it.
Thhank you Sir for this video.it's very interesting.but what are you doing here we had seen it in our Primary school.i am a Moroccan Pharmacist.i can assure you that here in Morocco we have a higher level of education than you watching to this video i'm surprised that you Pharmasicts are using this technics to calculate. NB:i hav a Russian Diploma of Pharmacy.i can assure you that Education level and Knowledge are higher than in Morocco & USA sooooo much.
Lol this is for Pharm technicians not the Pharmacists😂..to be a pharmacist in the USA can take almost up to 8 years. Pharmacists know about medications more than the doctors.
Please help me with this one, and tell me how I can learn to solve this problems? I am getting so confuse. Thanks again. A patient needs IV infusion of 0.9% NaCl. You have water for injection and 4.5%w/v stock solution of NaCl. There are no displacement volume effects. How much of the 4.5% w/v needs to be added to a 1L WFI bag to produce the desired concentration? A. 700mL B. 250mL C. 350mL D. 500mL
Hi Ana. This is best solved using the box method for alligatioins. It would be easier to draw the box if you would send me an email at brad.wojcik@gmail.com. Normally in these problems you know the total amount of solution you are making, but not the amount of each strength. On this one you don't know the total amount that you will be making, but you know the amount of one of the strengths. Draw a box with 0 in lower left, 4.5 in upper left, 0.9 in upper right and 3.6 in lower right. You will have 3.6 parts out of 4.5 parts of 0%. Since you don't know the total amount, the equation will be (3.6/4.5)(x)= 1000 mL. Solving for x you get 1250 mL. This will be the total of the 4.5% and the WFI. Since you know that the WFI is 1000 mL, the 4.5% would be 250 mL. I know this is a little more confusing than seeing it drawn out.
I just started a job as an OET at a specialty pharmacy and just found out that I will need to become certified in 7 months. Do you have complete training material for this? I like your pharmacy calculation video very much!
Hi Dr. Brad, thank you for your videos, I have learned a lot with them, but there is still something that I can not get it. Help me please with this exercise maybe you can help me. and thanks again. Methylprednisolone is available in 1 g vials, with instructions to add 15.6 mL of sterile water to the vial to obtain a total volume of 16 mL. How many mL will be required for a 875mg dose if the dose is added to 50 mL of D5W. A. 1.1 mL B. 0.8 mL C. 14 mL D. 16 mL
Hi Ana, This is a powder volume problem, but is actually pretty easy. It doesn't matter how many mL of sterile water you are adding to the vial or the fact that it will be added to 50 mL of D5W. All that matters is that you end up with 1 g of methylprednisolone in 16 mL of solution. Now you have to change the 875 mg into mL using the ratio of 16 mL/1 g. We can just change the 1 g to 1000 mg and we get 875 mg(16 mL/1000 mg) = 14 mL.
Hi Ana. I am always glad to help. There is a video on Powder Volume problems also. th-cam.com/users/edit?o=U&video_id=xWw2pQrnztU You can always email me questions at brad.wojcik@gmail.com if that is easier.
I need help with a problem have in my class now. I am trying to find how many doses are supposed to be dispensed. Ceclor 125mg/5ml 1 tsp every 8 hours for 10 days. Any advice would help.
Hi Delani. One dose is taken every 8 hours, so that is 3 doses/day. 10 days (3 doses/day) = 30 doses. They may ask how many mL to dispense. There are 5 mL to a tsp. 30 dose (5 mL/dose)= 150 mL.
I have another one. I really really need your help. Thank you. How many milliliters of a 1:2000 Drug "I" solution and a 7% Drug "I" solution mixed would make 120ml of a 3.5% solution of drug "I"? A. 54.6mL of 7% + 65.4mL of 1:2000 B. 59.6mL of 7% + 60.4mL of 1:2000 C. 20.0mL of 7% + 100 mL of 1:2000 D. 65.4mL of 7% + 54.2mL of 1:2000
Hi Ana. This is an alligetion problem where you have to use the "box" method. I don't know if you watched that video. First you have to change the 1:2000 from a ratio strength into a percentage strength. 1:2000 means 1 g/2000 mL. Multiply by 100% to change to a percent strength. 1 g/2000 mL (100%) = 0.05%. Now set up the box with 0.05 in the lower left corner, 7 in the upper left and 3.5 in the middle. This will give you 3.45 in the upper right and 3.5 in the lower right. There are 6.95 total parts (3.45 + 3.5). 3.45/6.95 parts are 7%. So 3.45/6.95 (120 mL) = 59.6 mL of the 7%. 3.5/6.95 (120 mL) = 60.4 mL of the 0.05% which is the 1:2000. These problems are hard to explain without drawing the box, but I hope you watch the video. th-cam.com/users/edit?o=U&video_id=CujuVNn7ROY
hi mr. Brad can u help with this problem. how many milliliters of water should be added to 1 pint of 70% solution to prepare a 30% solution? l know that 1 pint= 480ml. l did but l came up with 274.2ml but in my book is 1,120ml? thanks
+Ana Angel Hi Ana. Unfortunately, both you and the book are wrong. There are actually about 473 mL in a pint, but most people us 480 mL, so we will use 480 mL. You can do this two ways. If you use the formula V1C!=V2C2 where V1 is the volume of one of the solutions and C1 is the concentration of that solution and V2 and C2 are the volume and concentrations of the other solution, you get: 480 mL(70%)=V2(30%) Solving for V2 you get 1120 mL. This is the total volume of the second solution, not how much you had to add. You started with 480 mL, so you had to add 640 mL. If you don't want to use the formula, calculate how many grams (we will assume it is w/v, but you would get the same answer if you use v/v) of active ingredient are in the pint of 70% then calculate how many mL of 30% solution you can make with those grams. 480 mL(70g/100mL)= 336 g. 336 g(100 mL/30g)= 1120 mL. Hope this helps.
Pls Hw can I calculate the percentage weight per volume of an antacid give below Ulglcld suspension it contains 15ml magnesium hydroxide 250mg Aluminium hydroxide 250 calculate the percentage weight per volume of each one
Hi. The % w/v is %g/mL. 250 mg/15 mL is 0.25 g/15 mL. Now just add the % sign by multiplying by 100%.(0.25 g/15 mL) (100%) =1.7% w/v. Both ingredients would be the same percentage.
Maybe the c's are zeros? It still wouldn't make much sense with that dosage. And nobody uses T for tablets. i.e., would just write Sig: 1-2 po...not 1-2T po
Hi there, not sure if you'll get back to me on time, but can you help me with this question: How many mL of a 2% w/v stock solution is required to prepare 200 mL of a 1:5000 solution Thank you, Mary
+MMike Hi Mary, I think the easiest way to do this is to calculate how many grams of the active ingredient you need in the 200 mL of the the 1:5000 solution. 1:5000 means 1 g in 5000 mL of solution. You have 200 mL, so 200 mL(1 g/5000 mL)= 0.04 g. Now you go shopping for your 0.04 g. You will get that from the 2% stock solution, which is 2 g/100 mL. 0.04 g(100 mL/2 g) = 2 mL. You can also convert the 1:5000 into a percentage and use V1C1=V2C2. (1/5000)(100%)=0.02% 200 mL(0.02%)=x(2%) Solving for x you get 2 mL. Be sure to watch the video on percents, percent strength and ratio strength. th-cam.com/video/8qDVEtrQ8a4/w-d-xo.html
MMike You don't have to use V1C1=V2C2. I usually use V1C1 as the volume and concentration that you know both V&C and use V2C2 for the solution in which you know only V or C. I think in that previous answer I used X instead of V2, but you get the same answer.
I tried for 2 hours to solve this one, and I couldn't. If 60 grams of 1% Ointment "L" is mixed with 80 grams of 2.5% Ointment "L", what is the % of Ointment "L" in final mixture? A. 2.14% B. 1.86% C. 1.73% D. 1.25%
If you need to cancel units, you put the ratios in so that the units are opposite of what is in place. For example, if mg are on top and you need to cancel them, then the mg in the ratio would be on the bottom.
Like this problem the np has ordered 100 mg IM bid of a drug which is available in 5 ml vials labeled 80mg/ml. How many ml will be administered per dose?
Hi Julie, Do you have a specific question about dimensional analysis? Basically, you are multiplying by a form of 1 to change the units from the units of what you are starting with to the units of the answer. It is explained at around 4:20 in the video.
I'm getting a little confused on how to set it up... I know how to do ratio and proportion it seems easier to me but I would like to under stand this method also.
www.dropbox.com/s/jg5dywv9bqi2f4e/Pharm%20120%20Handouts%20Book%20third%20ed%20Jan%202013nh.docx?dl=0 You can download my handout book here.Look over the section on dimensional analysis and see if it helps. It would be easier than thring to explain it here.
please i need the breakdown of how to solve this; solve this ;a dose is written for 5mg/kg every 12hours for three days. the adult to take this medication weighs 120 pounds. how much drug will be needed to fill this order. Thanks
Probably the easiest way to do this is calculate the amount needed for one dose, then multiply that by 6 (2 doses per day times 3 days). You are starting with 120 lb and you have to end up with mg. The ratios you will use to change the 120 lb pt weight to mg of drug are 1 kg/2.2 lb and 5 mg/kg. 120 lb (1 kg/2.2 lb)(5 mg/kg) = 272.7 mg. Now multiply 272.7 mg by 6 and you get 1636.2 mg. Hope this helps.
it sure did help. i was getting 1635 and wanted the exact values which you got. so grateful, but please another question, how much NaCL is in the following IV bag; D 5 1/2 NS 250ml (NS is 0.9% NaCl)
On this one you are starting with 250 mL and have to change that to mg. The ratio you will use is 0.45%. There is a video on percent strength that might help. 0.45% means 0.45 g/100 mL. 250 mL (0.45 g/100 mL) = 1.125 g.
the options didn't correlate with your answer. The answer like the book claimed was 1.25g but without explanation. Please can you help me with the video you suggested?
The NaCl solution is 0.45% w/v, which means the NaCl is weighed out and the water is measured in mL. You can change w to g and v to mL. Now you have 0.45% g/mL. To remove the % sign, divide by 100%. This is how you get 0.45g/100 mL. This is the ratio you will use as a tool to change 250 mL into g. 250 mL (0.45 g/100 mL = 1.125 g. The mL cancel out.
+Miss De Nogla you are right that's an error. 4cc means 4ml, not such thing as 4cc mg lol... These books have a lot of errors too... That's why a classroom setting is great..
1-5% means in each 100 ml solution there is 5 mg NaCl 2-we must convert mg to gm so,5 mg = 0.005 gm. 3- No. of mls = 100*100/0.005=2,000,000 mls. I hope that can help you@Janet Mendoza
Hi Janet. Sorry, I didn't see this question earlier. 5% means 5 g/100 mL (not 5 mg/100 mL). You are starting with 100 g and have to end up with mL. The ratio you will use to change g to mL is 100 mL/5 g. 100 g(100 mL/5 g) = 2000 mL
Hi Mike. Thanks for the comment. What I said in the video is that 1000 mg divided by 1 g equals 1. I know it seems strange that this is true. You could replace the 1000 mg with 1 g, then you would have 1 g divided by 1 g equals 1. You can download my book at payhip.com/b/5xVY . Let me know if you have any questions.
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Your videos are what helped me pass my Certification Exam. Thank you so much. Keep it up!!
So glad I could be of help! Congratulations!
i got 20 calculation questions in my exam and 18 of those attempts were correct..and for each of my correct answer i give you the credit coz i followed all your vids before my exam and practised..I freaked out before but as i began to practise from your vids...it made me very easy to understand..all i can do is pray for u from my heart that you are doing such a great job and a big thankyou!!! and my advice to fellow test takers is that dont freak out like i was very worried before...just practise out from this channal and i swear ull feel a lot of confidence building in you ...his way of explaining is excellent so just his vids are enough for you to learn thoroughly..! ALL THE BEST :)
Hi Fistful. Thanks for the nice comment. For some reason this comment got routed to spam and I just saw it. Let me know if you have any questions.
So glad I found this. Thank you!
This is fantastic; I appreciate the actual explanation of the technique being used (e.g. dimensional analysis) instead of just steam rolling through the problem.
Brad the hands on I will have to go on the campus. thanks for responding back with me.
Thank you for posting your videos. You are my life saver.
Thank you!, Thank god i found your Videos, the way you calculate is just amazing and simple, cant believe i was trying to memorize all those formulas when i can do this instead. Props to you doctor!
Thank you for the nice comment. Now you can go back to your class and show them how easy they are.
Sure thing! I just took the ptce and passed!!. I would have been doomed if i had not learned your method, over 25% was math problems i could solve this way.
Yayyy I got 5.1 when I first worked it out! I still watched the rest of the video and it was very well explained; I will definitely use this method to solve more complicated problems though. Thank you!
Instablaster
Hi Ana, I will do this when I get home later. Basically, you have to calculate the total weight of the active ingredient from both ointments and the total weight of the final product, then change that to a percentage.
You are most welcome. Be sure to download the handout book and exercises on the main page.
-Dr. Brad
This video just kept me from a panic attack from my studies! Lol Thanks for showing what my course video didn’t!
Hi Jeffrey. The three problems you asked about are all solved the same way. Each problem has three parts to it: 1) A given, the units of the answer, and one or more ratios. In each problem start by writing down the given ( 0.075mg/day for the first problem, 8 oz for the second problem, 10 mL for the third problem) and the units of the answer for each: mg/h, days, days. For problem 1) 0.075mg/d = mg/h, you can see that you only have to change days to hours. You will do that with the conversion factor 1 day/24 h. (0.075 mg/d)(1 day/24 h) = 0.003125 mg h. Of course you could just write it as 0.075 mg/24 h and divide it out. Problem 2) 8 oz = days. On these problems, I usually tell my students to calculate how much per day so you can cut down on the number of ratios in the problem. 8 oz (1 day/8 tsp)(6 tsp/ 1 oz) = 6 days. See how all of the unwanted units cancel out? Problem 3) 10 mL = days. The ratios you will need are 100 units/mL and 1 day/60 units.
10 mL(100 units/mL)(1 day/60 units) = 16.7 days. It doesn't matter that 2 vials are dispensed because they are asking how long 10 ml will last. This method may seem a little harder than other methods at first, but once you learn it you will be able to do most all problems that do not involve mixing or dilutions. Sometimes it is kind of hard to determine what the given is in the problem, but with a little practice you will learn to recognize it. Let me know if you have any other questions.
You are welcome.
Never mind! I watched the video!! Thank you!!!
Glad I could help. Let me know if you have any questions.
+Brad Wojcik I figured out when I should times or divide based on the Kg,G,Mc,Mcg scale. Pretty cool. I just hope that I pass this test. I am studying 200 prescriptions: the Generic Name- Brand Name- Purpose- and their DEA schedule type. I know that I need to know the laws.... Medical Acts... I probably just need to borrow the "Orange Book" from a pharmacy.. Pharmacy Laws... Common Abbreviation.... Codes.. All of this information I need to remember
Thank you so much, you really explained how to break down the problem, I also like the dimensional analysis method as it shows the full problem and allows you to check for any errors, as I'm studying for my PTCB exam, your videos have been very helpful!
Hi Courtney,
Thank you for the nice comment. You should learn both dimensional analysis and ratio proportion, but you should also know that chemists, physicists and engineers all use the dimensional analysis method of solving their problems. For some reason, the medical community and pharmacy community use the ratio proportion method. Be confident that if you use dimensional analysis, you are using the safest and most powerful method. I will probably get a nasty comment for this, but I don't care.
Dr. Brad
Glad I could help!
Are students allow to use calculator sitting for license exam? As well as in class?
I like your first method better, it took me about 2 weeks to get the ratio/proportion formula down and familiar with it.
Hi Celina. I think the first way, dimensional analysis, is easier also. Chemists, physicists, engineers all use this method because it is easier and more powerful. For some reason the medical and pharmacy community use the ratio proportion method. You should learn both.
Thank you for simplifying this for me.
Glad I could help!
Dear Dr. Brad, i sent you a message just now regarding confusion on setting up a particular dimensional analysis set up. I would love it if you would create a video that covered this simple (yet confusing to me in this moment) problem to show WHICH pieces to fit in the puzzle are needed and which are not. thank you!!
Thank you so much for your videos!
You are welcome!
Thank you so much!!!
Very very easy. Solved this with my eyes closed
You explain better than my actual professor. :(
I decided to be a Pharmacy technician as my career and this is my first semester on learning all these new calculations. and these videos def help me. But right now its all sorta confusing especially remembering how many liter or milliliter in an ounce for example
Hi Danny,
You will learn that quickly.
-Dr. Brad
easier said than done haha but do u have videos on medicine and weights like converting?
Hi Danny,
Be sure to view the introduction video. Also, download my book from the main page.
-Dr. Brad
Hello! your videos are easy to follow bc the way you explain things. Im taking my exam this week and trying to brush up on IV calculations. Im trying to memorize these formulas but i don't understand when to use which. The book im using has infusion rate AofF times gtt/ml over Hrs to Admin times 60min/hr. Theres frequency schedule total vol infused over IV rate and IV rate vol infused over infusion time and drip rate vol infused over infusion time multiplied by drip set factor. sorry my msg is long im just really confused 😕 I understand when theyre doing the calculations but some seem similar so I don't know when to use what and why.
great example. thankyou
Thanks for the nice feedback. I am glad that I could help.
You can download my book, Pharmacy Calculations for Pharmacy Technicians: Solving Pharmacy Calculation Problems Without All the Silly Formulas, for free at payhip.com/b/5xVY. It goes into more detail than possible on the videos and is full of practice problems and answers.
HI Kat,
You are welcome. Let me know if you have any questions on specific problems.
Brad Wojcik Hello Dr i went to study pharmacy so in the beginning what i will do please Dr
I didn't see "divide into 4 doses" and when I got 20.5 mL I though it was wrong, but that is the daily does. I also rounded to the nearest unit when figuring the Pt's weight in kg. which got me 82 kg. rather than 81.8 kg. Should you round to the nearest tenth when doing the PTCB exam?
The proportion method has always been a favorite of mine to use in the pharmacy but the dimensional analysis method was also great to learn. Thanks for your videos!
Hi Miss De Nogla,
I would go out to the tenth of a kg.
Dr. Brad
Can you tell me how much morphine would a person be taking daily or every five hours if their drug test says 3000 ml . Every time my doc test me see freaks out and I know I'm taking my meds as prescribed. I have to keep them on schedule or I get a bad headache. This meaning I don't take more than what's prescribed. I never ever double up, if anything I can go without the rneds for several hours past my dosing time but like I said if I do that I get a headache so I keep them as close to the prescribed time frame as possible.
I'm starting to wonder if the drug is showing up in high doses due to other possible reasons like maybe my liver isn't precessing the drug properly or maybe I'm not drinking enough water or fluids and it's building up in my system. I'm a chronic pain patient and take it for all over pain , spinal pain fibromyalgia head and neck, hip pain. I hurt all over but every time she test me she tries to take away my meds I've even cut back in order to make sure I have a couple of days on hand in case she's out of the office when my refills are due or sometimes the pharmacy doesn't have the meds in stock in order to fill my script and I'll have to wait.
I've never taken more than I'm supposed to. I don't do street drugs either . Never been to jail never want to go so I always use my medication as prescribed, my dog can call me any time and I'll have my meds. I can't for the life of me figure out why she keeps trying to cut my meds back or take me off them when I hurt so bad. I've been in 2 car wrecks neither my fault, one a teenager hit me head on after changing her mind in an intersection she decided not to turn left and jumped back into the oncoming Lane and hit me head on said she was sorry she was speeding and late to a job interview. Because I'm so short the seat belt wraps around my neck really did a number on me. The other an elderly lady hit me head on while she was driving in the wrong lane through a construction area, her kids apologized said they needed to take her license away. I was later hit on top of the head with a Ford aerostar hatch, it hit me so hard it knock me to my knees and blacked out. I've been hit behind twice by you teenagers while I was just sitting at stop lights. And I had a bad overuse injury at a job that I received a settlement for. I live in severe neck & spinel pain everyday all day it never goes away.
I need your help trying to figure out what's going on. The only thing I can come up with is maybe the meds are building up in my system .
I think it said I had 3000 ml so what would that calculation be in mg tablets per day?
Sorry so long winded but I may need to show this to my doctor. I'm hoping to figure out what's going on and why. Thank you kindly
Hi, that is not something I am able to calculate. I wish you well.
Brad
@@BradWojcikPharmD thanks for reply. What if I gave you the amounts prescribed like 15 mg 5x day would equal how many ng/ml .
@@Lady-Carmakazi I don't think it is possible to calculate that.
@@BradWojcikPharmD hmm I must be misunderstanding the way it works. Thank you take care
I wish in these videos when your doing the math on the calculator that you would have put it on the board, I’m very new at this and it would help me I did however I did go back and watch the video twice it’s the nice thing about video learning , my question is now it’s 2017 how long are videos going to be good for on TH-cam for pharmacy technician knowledge some I’ve watched are older ones are any too old to be watching ? Or has the ways of doing these calculations not changed in over 10 years ?
Hi Trisha. The math in these videos will never change. If you have any specific questions please email me at brad.wojcik@gmail.com.
Thank you Dr. Brad, I've being practicing with powder volume and I think I got it. but suddenly there is another problem and I got confuse again. This is not powder because I need 3 values and there is not my 3 values. and its not an allegation problem
HOW MANY MILLITERS OF A 3% (W/V) WILL BE NECESSARY TO MAKE 6OZ OF A 1:200 SOLUTION?
A.
30 ML
B.
180 ML
C.
25 ML
Hi Ana. First off you to know how to change the 3% w/v and 1:200 into ratios which contain g and mL. 3% w/v is 3 g/100 mL and 1:200 is 1 g/200 mL. If you don't know how to do that, I can send you some info. Just email me at brad.wojcik@gmail.com. First step in the problem is to calculate how many g you will need to make the 6 oz of 1:200 solution. You have to change 6 oz into g using ratios as tools. 6 oz (30 mL/oz)(1 g/200 mL)= 0.9 g. Now calculate how many mL of the 3% solution you need to get the 0.9 g. Here you will change g into mL. 0.9g (100 mL/3 g) = 30 mL You could also use V1C1=V2C2 by changing 1:200 into 0.5% v1(3%)=180 mL(0.5%) Solving for V1 you will get 30 mL. Hope this helps.
-Brad
Thank you Dr.Brad again. But instead of multiply 6 oz times 30 I was counting as 600 ml, that's why I could not do it. and V1C1=V2C2 was my first option and off course the answer was wrong. I apologize again.
Hi Ana. I am glad you understand it. No need to apologize!
Hi Ana. For some reason, I couldn’t find you question on the comments, so I am replying here. The question was if you mix 60 g of a 1% ointment is mixed with 80 g of a 2.5% ointment, what is the % of ointment in the final mixture. You have to calculate the total grams of the active ingredient in both ointments and the final weight of the two ointments after they are mixed, then change that back to a percentage. 60 g oint (1 g active ing/100 g oint) = 0.6 g 80 g oint (2.5 g active ing/100 g oint) = 2.0 g. You have 2.6 g active ing in 140 g of oint. 2.6 g a.i. /140 g oint (100%) = 1.86% Also, it is easier if you just email me at brad.wojcik@gmail.com
hi Brad do you think that taking pharmacy technician is harder online than in classroom setting.
+Elaine Jones Hi Elaine. I think it would be much more difficult taking it online as you would not have any hands on experience working with IV products, etc.
Hi, I am very curious as to why pharm. techs are doing calculations and not the pharmacist? I would think it would be dangerous for a pharm. tech to do this and not the person with the PhD. Thanks for your reply.
Hi remarkable. Calculations are part of the tech's job, but everything should be checked by the pharmacist.
Well I’m new at this pharmacy technician college education and I feel that the pharmacists have enough to do so we do what they use to do and it’s great for us we do a lot of the work for them but they did it all to at some point in time it seems because here he is teaching us...
remarkable937 it’s stupidly easy math though... pharmacy techs can do it. It’s basic algebra I.
Here in Hungary the pharmacist does the calculations, the technicians job is to take phine calls, organize medication in alphabetical order and by order of expiration date bring the prescriptions to the pharmacist who will make it and also to take in the orders for medications in the morning. More experienced technicians (after 3 years of work) are allowed to expedite and to help with packaging the medication that te pharmacist makes and also they can help the pharmacist under the pharmacist supervision in dosing medication
I know just as much to the regular joe as a pharm tech but the process is the pharm tech does the calcs and then the pharm d checks the calc and then the pharm tech takes the corections or calcs and performs the grunt work for the sig it a simple mechanic of process called "better than a computer taking all the work out of it instead a less payed person ".
Hi Mr.Brad. Could you please help with this problem? What volume of a 1 in 400 v/v solution is needed to produce 5L of a 1 in 2000 v/v solution? I am not able to do that from the first method?
You can do it a couple of ways. First calculate number of grams in 5 L of the 1:2000 solution then calculate the volume of the 1:400 solution needed to get those grams.
5 L(1 g/2000 mL) (1000 mL/L) =2.5 g. 2.5 g (400 mL/1 g) =1000 mL. You can also use V1 C1 = V2 C2.
question?
as we all know in pharmacy we use the metric measuring system. There are several ways how the metric system differs from common household measures. what could be the advantages and disadvantages of each system? and why the metric system is preferred in the pharmacy.
Hi Syeda. The metric system is much easier to use and there is no ambiguity on the units, as there are with household measurements. For example, a teaspoonful can vary depending on how you are measuring it.
Thhank you Sir for this video.it's very interesting.but what are you doing here we had seen it in our Primary school.i am a Moroccan Pharmacist.i can assure you that here in Morocco we have a higher level of education than you watching to this video i'm surprised that you Pharmasicts are using this technics to calculate.
NB:i hav a Russian Diploma of Pharmacy.i can assure you that Education level and Knowledge are higher than in Morocco & USA sooooo much.
Lol this is for Pharm technicians not the Pharmacists😂..to be a pharmacist in the USA can take almost up to 8 years. Pharmacists know about medications more than the doctors.
Please help me with this one, and tell me how I can learn to solve this problems? I am getting so confuse. Thanks again.
A patient needs IV infusion of 0.9% NaCl. You have water for injection and 4.5%w/v stock solution of NaCl. There are no displacement volume effects. How much of the 4.5% w/v needs to be added to a 1L WFI bag to produce the desired concentration?
A. 700mL
B. 250mL
C. 350mL
D. 500mL
Hi Ana. This is best solved using the box method for alligatioins. It would be easier to draw the box if you would send me an email at brad.wojcik@gmail.com. Normally in these problems you know the total amount of solution you are making, but not the amount of each strength. On this one you don't know the total amount that you will be making, but you know the amount of one of the strengths. Draw a box with 0 in lower left, 4.5 in upper left, 0.9 in upper right and 3.6 in lower right. You will have 3.6 parts out of 4.5 parts of 0%. Since you don't know the total amount, the equation will be (3.6/4.5)(x)= 1000 mL. Solving for x you get 1250 mL. This will be the total of the 4.5% and the WFI. Since you know that the WFI is 1000 mL, the 4.5% would be 250 mL. I know this is a little more confusing than seeing it drawn out.
I just started a job as an OET at a specialty pharmacy and just found out that I will need to become certified in 7 months. Do you have complete training material for this? I like your pharmacy calculation video very much!
Hi Norma. I don't have material for a complete course, just the math, which can be downloaded from the main channel page.
Hi Dr. Brad, thank you for your videos, I have learned a lot with them, but there is still something that I can not get it. Help me please with this exercise maybe you can help me. and thanks again. Methylprednisolone is available in 1 g vials, with instructions to add 15.6 mL of sterile water to the vial to obtain a total volume of 16 mL. How many mL will be required for a 875mg dose if the dose is added to 50 mL of D5W.
A. 1.1 mL
B. 0.8 mL
C. 14 mL
D. 16 mL
Hi Ana, This is a powder volume problem, but is actually pretty easy. It doesn't matter how many mL of sterile water you are adding to the vial or the fact that it will be added to 50 mL of D5W. All that matters is that you end up with 1 g of methylprednisolone in 16 mL of solution. Now you have to change the 875 mg into mL using the ratio of 16 mL/1 g. We can just change the 1 g to 1000 mg and we get 875 mg(16 mL/1000 mg) = 14 mL.
Thank you so much. I guess all that about 50mL confuse me a lot. thanks again.
Hi Ana. I am always glad to help. There is a video on Powder Volume problems also. th-cam.com/users/edit?o=U&video_id=xWw2pQrnztU You can always email me questions at brad.wojcik@gmail.com if that is easier.
what happen physically when you cancel out units
I need help with a problem have in my class now. I am trying to find how many doses are supposed to be dispensed. Ceclor 125mg/5ml 1 tsp every 8 hours for 10 days. Any advice would help.
Hi Delani. One dose is taken every 8 hours, so that is 3 doses/day. 10 days (3 doses/day) = 30 doses. They may ask how many mL to dispense. There are 5 mL to a tsp. 30 dose (5 mL/dose)= 150 mL.
Thank you so much
You are welcome. You can also email me questions at brad.wojcik@gmail.com if you need help.
I have another one. I really really need your help. Thank you.
How many milliliters of a 1:2000 Drug "I" solution and a 7% Drug "I" solution mixed would make 120ml of a 3.5% solution of drug "I"?
A. 54.6mL of 7% + 65.4mL of 1:2000
B. 59.6mL of 7% + 60.4mL of 1:2000
C. 20.0mL of 7% + 100 mL of 1:2000
D. 65.4mL of 7% + 54.2mL of 1:2000
Hi Ana. This is an alligetion problem where you have to use the "box" method. I don't know if you watched that video. First you have to change the 1:2000 from a ratio strength into a percentage strength. 1:2000 means 1 g/2000 mL. Multiply by 100% to change to a percent strength. 1 g/2000 mL (100%) = 0.05%. Now set up the box with 0.05 in the lower left corner, 7 in the upper left and 3.5 in the middle. This will give you 3.45 in the upper right and 3.5 in the lower right. There are 6.95 total parts (3.45 + 3.5). 3.45/6.95 parts are 7%. So 3.45/6.95 (120 mL) = 59.6 mL of the 7%. 3.5/6.95 (120 mL) = 60.4 mL of the 0.05% which is the 1:2000. These problems are hard to explain without drawing the box, but I hope you watch the video. th-cam.com/users/edit?o=U&video_id=CujuVNn7ROY
hi mr. Brad can u help with this problem. how many milliliters of water should be added to 1 pint of 70% solution to prepare a 30% solution? l know that 1 pint= 480ml. l did but l came up with 274.2ml but in my book is 1,120ml? thanks
+Ana Angel Hi Ana. Unfortunately, both you and the book are wrong. There are actually about 473 mL in a pint, but most people us 480 mL, so we will use 480 mL. You can do this two ways. If you use the formula V1C!=V2C2 where V1 is the volume of one of the solutions and C1 is the concentration of that solution and V2 and C2 are the volume and concentrations of the other solution, you get: 480 mL(70%)=V2(30%) Solving for V2 you get 1120 mL. This is the total volume of the second solution, not how much you had to add. You started with 480 mL, so you had to add 640 mL. If you don't want to use the formula, calculate how many grams (we will assume it is w/v, but you would get the same answer if you use v/v) of active ingredient are in the pint of 70% then calculate how many mL of 30% solution you can make with those grams. 480 mL(70g/100mL)= 336 g. 336 g(100 mL/30g)= 1120 mL. Hope this helps.
+Brad Wojcik I'm new to this and and studying for my PTCB exam.. I need to know what Math Steps Are Being Submerged To Get the Answers?
Pls Hw can I calculate the percentage weight per volume of an antacid give below Ulglcld suspension it contains 15ml
magnesium hydroxide 250mg
Aluminium hydroxide 250 calculate the percentage weight per volume of each one
Hi. The % w/v is %g/mL. 250 mg/15 mL is 0.25 g/15 mL. Now just add the % sign by multiplying by 100%.(0.25 g/15 mL) (100%) =1.7% w/v. Both ingredients would be the same percentage.
The question came from a Sample Prescription from a Dosage Calculation Module Lesson via HealthEdToday.
Maybe the c's are zeros? It still wouldn't make much sense with that dosage. And nobody uses T for tablets. i.e., would just write Sig: 1-2 po...not 1-2T po
Hi there, not sure if you'll get back to me on time, but can you help me with this question:
How many mL of a 2% w/v stock solution is required to prepare 200 mL of a 1:5000 solution
Thank you,
Mary
+MMike Hi Mary,
I think the easiest way to do this is to calculate how many grams of the active ingredient you need in the 200 mL of the the 1:5000 solution. 1:5000 means 1 g in 5000 mL of solution. You have 200 mL, so 200 mL(1 g/5000 mL)= 0.04 g. Now you go shopping for your 0.04 g. You will get that from the 2% stock solution, which is 2 g/100 mL. 0.04 g(100 mL/2 g) = 2 mL. You can also convert the 1:5000 into a percentage and use V1C1=V2C2. (1/5000)(100%)=0.02% 200 mL(0.02%)=x(2%) Solving for x you get 2 mL. Be sure to watch the video on percents, percent strength and ratio strength. th-cam.com/video/8qDVEtrQ8a4/w-d-xo.html
i'm getting all confursed with this stupid c1v1=c2v2 crap. I mess up in what's first and second. Also, when there's ratios ..
Thank you soo much!! yes i got 2ml,
the answer concentration is 1/50, how do i get that
MMike You don't have to use V1C1=V2C2. I usually use V1C1 as the volume and concentration that you know both V&C and use V2C2 for the solution in which you know only V or C. I think in that previous answer I used X instead of V2, but you get the same answer.
The 2% solution is 1:50 because it is 2 g/100 mL or 2:100, which reduces to 1:50
I tried for 2 hours to solve this one, and I couldn't.
If 60 grams of 1% Ointment "L" is mixed with 80 grams of 2.5% Ointment "L", what is the % of Ointment "L" in final mixture?
A. 2.14%
B. 1.86%
C. 1.73%
D. 1.25%
1.86%
I prefer the first method !
I’m terrible at math. Does being bad a math mean that I’m completely screwed from being a tech? Please respond. Thank you.
You will probably have to pass a test, but if you practice a little it really isn't that difficult.
Brad Wojcik thank you so much for your response! You’re awesome!
How do you know which way to place the ratios im confused and getting them wrong because of that
If you need to cancel units, you put the ratios in so that the units are opposite of what is in place. For example, if mg are on top and you need to cancel them, then the mg in the ratio would be on the bottom.
Do you only look at the given and that will tell you the next steps to make
@@bryannpowell4953 You can start with the given and the units of the answer. That way you can work from either end.
Now im having a problem with the extra information in the problem and just knowing what the problem is asking me and including the right ratio
Like this problem the np has ordered 100 mg IM bid of a drug which is available in 5 ml vials labeled 80mg/ml. How many ml will be administered per dose?
2:07
I get a little confused using dimensional analysis... Can you help me understand it better? Please.
Hi Julie,
Do you have a specific question about dimensional analysis? Basically, you are multiplying by a form of 1 to change the units from the units of what you are starting with to the units of the answer. It is explained at around 4:20 in the video.
I'm getting a little confused on how to set it up... I know how to do ratio and proportion it seems easier to me but I would like to under stand this method also.
www.dropbox.com/s/jg5dywv9bqi2f4e/Pharm%20120%20Handouts%20Book%20third%20ed%20Jan%202013nh.docx?dl=0
You can download my handout book here.Look over the section on dimensional analysis and see if it helps. It would be easier than thring to explain it here.
Thank you Dr. Wojcik!!
www.dropbox.com/s/7hoqbtimvpo2kn8/Week%203%20Exercises%20combined%20with%20answersnh.docx?dl=0
You are welcome. Here are some exercises.
please i need the breakdown of how to solve this; solve this ;a dose is written for 5mg/kg every 12hours for three days. the adult to take this medication weighs 120 pounds. how much drug will be needed to fill this order. Thanks
Probably the easiest way to do this is calculate the amount needed for one dose, then multiply that by 6 (2 doses per day times 3 days). You are starting with 120 lb and you have to end up with mg. The ratios you will use to change the 120 lb pt weight to mg of drug are 1 kg/2.2 lb and 5 mg/kg. 120 lb (1 kg/2.2 lb)(5 mg/kg) = 272.7 mg. Now multiply 272.7 mg by 6 and you get 1636.2 mg. Hope this helps.
it sure did help. i was getting 1635 and wanted the exact values which you got. so grateful, but please another question, how much NaCL is in the following IV bag; D 5 1/2 NS 250ml (NS is 0.9% NaCl)
On this one you are starting with 250 mL and have to change that to mg. The ratio you will use is 0.45%. There is a video on percent strength that might help. 0.45% means 0.45 g/100 mL. 250 mL (0.45 g/100 mL) = 1.125 g.
the options didn't correlate with your answer. The answer like the book claimed was 1.25g but without explanation. Please can you help me with the video you suggested?
The NaCl solution is 0.45% w/v, which means the NaCl is weighed out and the water is measured in mL. You can change w to g and v to mL. Now you have 0.45% g/mL. To remove the % sign, divide by 100%. This is how you get 0.45g/100 mL. This is the ratio you will use as a tool to change 250 mL into g. 250 mL (0.45 g/100 mL = 1.125 g. The mL cancel out.
Thank you so much, this helps a lot. :)
Here is a dosage calculation I find very vague and confusing: Rx: Aspirin 4cc mg Sig" 1-2T po q6hr prn pain, Disp: #6c
That doesn't make any sense. Was it from a book?
carrie walls Yeah, that looks like an error. "4cc mg"?
+Miss De Nogla you are right that's an error. 4cc means 4ml, not such thing as 4cc mg lol... These books have a lot of errors too... That's why a classroom setting is great..
I have a question
Hi Janet. What is the question? You can reply here or email me at brad.wojcik@gmail.com.
I have a problem I can't solve it reads hom many mls of 5% sodium chloride solution can be prepared from 100 gms of sodium chloride?
1-5% means in each 100 ml solution there is 5 mg NaCl
2-we must convert mg to gm so,5 mg = 0.005 gm.
3- No. of mls = 100*100/0.005=2,000,000 mls.
I hope that can help you@Janet Mendoza
Mohamed Elsayed yes that makes alot of sence i am trying to take my nationals for pharm tech and i need all the help i can get thank you
Hi Janet. Sorry, I didn't see this question earlier. 5% means 5 g/100 mL (not 5 mg/100 mL). You are starting with 100 g and have to end up with mL. The ratio you will use to change g to mL is 100 mL/5 g.
100 g(100 mL/5 g) = 2000 mL
1000 divided by 1 is 1000 and not 1
Hi Mike. Thanks for the comment. What I said in the video is that 1000 mg divided by 1 g equals 1. I know it seems strange that this is true. You could replace the 1000 mg with 1 g, then you would have 1 g divided by 1 g equals 1. You can download my book at payhip.com/b/5xVY . Let me know if you have any questions.