Hi Julie, I am glad that I was able to help you. Remember, the units are the most important part of the problem. They will always tell you how to solve the problem. The numbers just go along for the ride. Let me know if you have any specific questions. Also, you can download my handout book and exercises from the main channel page. -Dr. Brad
Hi Evans, First of all, it is always best to put a leading zero on your decimals. 0.25 rather than .25. If you multiplied 0.25 x 100 g you would have 25 g, right? Treat the % sign just like any other unit. Remember, 100% is the same as 1. Think about this a little and I think you will see that 0.25 x 100% is 25%. -Dr. Brad
If you want to change 50mg/5ml into a percent strength, the units of the answer will be %g/ml. You have to add the % by multiplying by 100% and you have to change 50mg into g by multiplying by 1g/1000mg. You don't have to do anything with the 5ml. 50mg/5ml (100%)(1g/1000mg) = 1%g/ml or 1% w/v
Hi Chirs, Since you are just mixing two solutions together you would just calculate 50% of the 500 mL for the Betadine and 50% of the 500 mL for the normal saline. It doesn't matter what the composition of the Betadine or NS is. The answer would be 250 mL of each. -Dr. Brad
These are all the videos I have at the moment. I should make some more. Be sure to watch the introduction video so that you see that most of the problems are worked the same. -Dr. Brad
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 Alejandra, Your answer will have the units of %g/ml. You are starting off with 2,250mg/L. You have to change mg to g, L to mL, and add the percent sign. 2,250mg/L (1 g/1000 mg) (1L/1000 mL) (100%) = 0.225% g/mL (or 0.225% w/v) See how the conversion factor of 1g/1000mg changes the 2,250 mg to g? The conv factof 1L/1000 mL) changes the L to mL. Multiplying by 100% adds the % sign. Always start by writing down the units of the answer then figure out how to change the units of your given.
You are most welcome. Let me know if you have any other questions. Remember, the units will guide you through any problems that involve conversions, dosage calculations, percentages, percent strength, ratio strength, or drip rates.
Ok how about how much silver nitrate ( in grams) must be used in preparing 600mL of a solution such that 20 mL diluted to 1L will yield a 1:5000 solution.
V/V questions seem to have been left out here, (because of their ease?) 500mL 50% betadine solution using normal saline _______ mL stock betadine; _______ mL normal saline. IS the answer simply 250mL of each? Or does the 0.9% for normal saline come into play?
Also, do you have any videos of you working test like questions? My pharmaceutical calculations teacher is really putting it on our class to say the least ha
Dr. Brad, I have a question. 1. What is the initial strength of a solution that is made by adding 200 mL of purified water to make 600mL of a 25% solution?
+Nikki Jackson Hi Nikki. First calculate how many grams of active ingredient you have in the 600 mL of 25% solution. 600 mL(25g/100 mL)=150 g. So you started off with 150g/400 mL. Now just change that to a percent by multiplying by 100%. (150g/400mL)(100%)=37.5% w/v
In the question we are adding 200 mL of purified water to a solution to make 600 mL of 25%, so we must have started with 400 mL in the original solution.
hello, I need help with this question I am stuck on , Threre are 2, 250 mg of NaCl in a L of a solution. What is the strength of the solution as a percent?
This is an edited comment which is actually replacing my original post because I was wrong. Brad's presentation shows and explains the topic extremely well.
Hi M Stephens.Thank for your comment.I know someone probably taught you to change a number to a percent by multiplying by 100, but if you multiply anything by 100, you are increasing its value by 100 times. So, (0.25)(100) = 25, not 25%. Whenever we convert units, we always multiply by a form of 1. For example, to convert 45 mg to g, we would multiply by (1 g/1000 mg) = 0.045 g. 1 g/1000 mg = 1 The same can be said about converting a number to a percentage. We want to multiply by a form of 1 so we don't change its value. 100% is 100/100, which is equal to 1. 0.25 (100/100) = 25/100= 25%. I hope this clears up any confusion. Dr. Brad
I think we both agree that 0.25 = 25%. Let's work backwards and find that value that we would multiply 0.25 by to get 25%. We will let x equal that value. 0.25 (x) = 25%. Solving for x we divide both sides by 0.25. 0.25(x)/0.25 = 25%/0.25 x = 100%. I would hope you keep an open mind and consider the fact that I may be right for the sake of your students.
M Stephens, Dr. Brad is also an instructor. There is no need to insult! He is absolutely correct in saying that you multiply by 100%. You include the percent so that it carries over into the answer! if you multiply a number by 100, then you just get a new number!! if you multiply by 100%, then you get a percent for an answer. Just look at your example! Your answer is wrong. 0.25 x 100= 25, not 25%.
Brad Wojcik Brad...I definitely have an open mind and, openly admit it when I make a mistake in class and out. Maybe we're not understanding one another. What I was saying was this: Let's say we have the fraction 1/4. To convert that into a decimal, it is 1 divided by 4 which equals 0.25 -- To convert 0.25 into a percent, we multiply it by 100 or move the decimal point two spaces right which gives us 25%, correct? Just as the ratio of 1:4 = 1/4, a 1:4 ratio = 25%. If a student gets 1 out of 4 questions right on a test, the student's score would be 25%...Do you agree or am I misinterpreting what you're saying? Thanks, Brad.
Christina Sanchez Yes, Christina..... 0.25 x 100 DOES = 25. Let's say you have 25% of a 4 fl.oz (120 mL) bottle of a suspension. That would mean you have 1 fl.oz (30 mL). But if we have 100% of a 4 fl.oz bottle of a liquid, we have 4 fl.oz or 100% of the 4 fl. oz of liquid....the same as multiplying by 1. Correct? Also, my apology if I came off a rude. I was tired and irritable when I posted that yesterday! I'm sure Brad DOES know his material. I think we may be misunderstanding each other. Thanks, Mike
I think the easiest way is to calculate the weigh of active ingredient needed to make the 60 oz first. 60 oz (1 g/200 mL) (30 mL/oz) =9 g. Now calculate volume of 3% needed. 9 g (100 mL /3 g) =300 mL.
How did u arrive to 100mg even though the answer jumps up at you because of the easy numbers. Can you show me what did u multiply and what did u divide? Je je The process is not quite clear to me. Thank you for your hep.
Hi Angela. Sorry, I was volunteering in Yosemite for a month and didn't have any internet. The units all canceled out except mg, so you multiplied 100 by 1, then divided by 1000, then multiplied by 1000 and divided by 1 to end up with 100 mg.
A physician prescribed an antibiotic to be mixed in white petrolatum to produce a 25% antibiotic preparation. The physician later changed the protocol to be only 12.5%. How much white petrolatum must be mixed with each 6 oz ointment container of 25% preparation to make the new 12.5% preparation? Calculate your answer in grams. This is a work book question but really doesnt make since. Can you help
Hi Emily. Thanks for the question. The ratio strength format is 1:another number, where another number is the amount of final product. In this case it is 1 g: mL of final product. What you have to start is 200 mcg:20 mL, but that is not the correct format. Start by changing 200 mcg to g. 200 mcg (1 g/1,000,000 mcg) = 0.0002 g. Now you can use either dimensional analysis or ratio proportion to find the number of mL which will contain 1 g. 200 mcg/20 mL = 1 g /x mL. Solving for x we get 100,000. So the answer is 1:100,000. Hope this helps! -Brad
sorry to bother you l have another word problem. the technician needs to prepare 2L of 0.25% acetic acid irrigation solution. the stock concentration of acetic acid is 25%. how many milliliters of sterile water have to be added?
+Ana Angel Hi Ana. It is never a bother to help students. You can do this a couple of different ways. You can use the formula V1C1=V2C2, where V1 is volume of the first solution, C1 is concentration of the first solution, V2 &C2 are volume and concentration of the second solution. We will say V1 &C1 are the 25% solution and V2C2 are the 2 L. We will change 2L to 2000 mL before we start. V1(25%)=(2000 mL)(0.25%) Solving for V1 we get (2000 mL)(0.25%)/25% = 20 mL, so you start with 20 mL of 25% and add 1980 mL of sterile water. The other way, without a formula, is to calculate how many grams of acetic acid are in the 2 L, then calculate how many mL of the 25% you need to get those grams. We will change 0.25% to 0.25g/100 mL (watch the % video if you didn't know that). 2000 mL(0.25g/100mL)= 5g. Now calculate how much 25% solution you need to get 5 g. 5 g(100 mL/25 g)= 20 mL. Hope this helps.
Hi Barb, This problem is similar to about 80% of the problems you will encounter in pharmacy math. It has three parts. 1) the units of the answer (mL), the given (1.5 g) and one or more ratios ( 50mg/mL and 1000mg/g)). Write down the units of the answer and the given with an = between them. 1.5 g = mL. Now arrange the ratios so that g gets canceled out and you end up with mL. 1.5 g ( 1000 mg/g)( 1 mL/50 mg) = 30 mL. It takes a little practice, but once you get the hang of it, these problems are very easy.Hope this helps. (p.s. Use g not gm) Dr. Brad
Also note that all the ratios can be turned upside down if necessary. I like to call ratios like 50 mg/ mL a custom ratio because it is only good for this problem. For this problem 1 mL of the solution will equal 50 mg. So, 1mL/50mg equals 1, also 50mg/1mL equals 1. For 1000mg/g and 1 g/1000mg, these both equal 1 because 1 g = 1000 mg and anything divided by itself = 1. So, what you are doing is multiplying 1.5 g by 1 twice to change the appearance. Ratios like 1000 mg/1 g I like to call off the shelf ratios because you can use them anytime they fit the problem and they always = 1. I hope this makes sense.
+Ana Angel It asked how many mL of sterile water had to be added to get the 2000 mL. You started with 20 mL of the 25% and had to add another 1980 mL of sterile water to get the 2000 mL.
WARNING: NO...to convert 0.45 to a percent, you multiply by 100 --NOT 100%. For those confused, the first 5 minutes of this video may confuse you more!
Hi Msk7046. Thank for your comment.I know someone probably taught you to change a number to a percent by multiplying by 100, but if you multiply anything by 100, you are increasing its value by 100 times. So, (0.45)(100) = 45, not 45%. Whenever we convert units, we always multiply by a form of 1. For example, to convert 45 mg to g, we would multiply by (1 g/1000 mg) = 0.045 g. 1 g/1000 mg = 1 The same can be said about converting a number to a percentage. We want to multiply by a form of 1 so we don't change its value. 100% is 100/100, which is equal to 1. 0.45 (100/100) = 45/100= 45%. I hope this clears up any confusion. Dr. Brad
Brad Wojcik Another way of thinking about this is asking yourself what you would multiply 0.45 to change it to 45%. You would set up the equation: 0.45x=45%. Solving for x you would divide both sides of the equation by 0.45. 0.45x/0.45 = 45%/0.45. x = 100% I hope this helps. -Dr. Brad
MSK7046, you are wrong! if you want convert any number to a percent you multiply by 100%!! The key is to have the percent sign so that it carries over to the number you are converting to a percent. If you do not include the percent, you just have a number multiplied by 100. Having the % sign converts your number. Same with converting a percent to a decimal, you divide the number by 100%, then the percent signs cancel out.
The ending is very confusing with his ratio brackets, he didn't explain how to change grams into mg very well, it wasn't clear...very dangerous system with Epinephrine , better off avoiding it and find a easier way...don't want to make a mistake..LOL...But thanks anyways
Hi Sassy. Thanks for the feedback. The introduction video goes into detail on changing grams into mg using the ratio of 1000 mg/g and cancelling out the grams. I suppose I should have explained it again here for those who didn't watch the introduction video. Also, I did say in the video that it was better to use the mg/mL strength printed on the label of the epinephrine rather than the ratio strength.
11yrs ago and here i am watching. It's my advance study lesson my 1st teacher in pharmacy😆
me too
Me too😂
8 years ago.
and me watching this year. Dr. Thank you for this video you're a legend.. Bless You!!
Hi Julie,
I am glad that I was able to help you. Remember, the units are the most important part of the problem. They will always tell you how to solve the problem. The numbers just go along for the ride. Let me know if you have any specific questions. Also, you can download my handout book and exercises from the main channel page.
-Dr. Brad
I am so glad that you make these videos, now I finally understand how to do this! Thanks Dr. Brad!!!
thank you so much Dr. Brad! All of your lectures helped me a lot! God bless you!
Thank you.... I am in a respiratory therapy program and needed a little help. I appreciate your wisdom
Dr.Brad you are greatly appreciated sir! Thank you for all your help and for making youtube videos to help us.
Thank you for turning an hour lecture to 10 mins boss man🙏🏾
Thank you so much Dr. Brad for sharing your knowledge and valuable information.
Hi Evans,
First of all, it is always best to put a leading zero on your decimals. 0.25 rather than .25. If you multiplied 0.25 x 100 g you would have 25 g, right? Treat the % sign just like any other unit. Remember, 100% is the same as 1.
Think about this a little and I think you will see that 0.25 x 100% is 25%.
-Dr. Brad
Hi Danna,
Thank you for the nice comment. Let me know if you need help on any specific problems.
-Dr. brad
If you want to change 50mg/5ml into a percent strength, the units of the answer will be %g/ml. You have to add the % by multiplying by 100% and you have to change 50mg into g by multiplying by 1g/1000mg. You don't have to do anything with the 5ml. 50mg/5ml (100%)(1g/1000mg) = 1%g/ml or 1% w/v
Brad Wojcik -Thank you. That wasn’t clear to me in the video, but this note helps to put it all together.
جاي نتابعك من العراق وكلشي ماافتهم وباجر فاينل
Hi Brian,
Thanks for the nice comment. These problems really are not that hard once you understand what you are actually doing.
-Dr. Brad
Thank you for including examples of each so that it makes sense!
Yeppers, too easy, Thanks Dr. Brad, very quick response!
These videos...... ❤❤ Just soo helpful, and we're extremely grateful 🙏
Thank you so much.Doctor Brad for this useful video ❤️❤️
Hi Jens,
Thanks so much for the nice comments. Let me know if you have any specific questions.
-Dr. Brad
Hi Chirs,
Since you are just mixing two solutions together you would just calculate 50% of the 500 mL for the Betadine and 50% of the 500 mL for the normal saline. It doesn't matter what the composition of the Betadine or NS is. The answer would be 250 mL of each.
-Dr. Brad
These are all the videos I have at the moment. I should make some more. Be sure to watch the introduction video so that you see that most of the problems are worked the same.
-Dr. Brad
Hi Dr. Brad, thank you for explaining/showing us how to calculate these problems. It really helped me! :)
Thank you for the help, Dr. Brad!
Thank you for thus video Dr. Brad. This is a big 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.
I’m Late !!!! But Thank You !!!! Your an awesome teacher !!!!
Hi Tiffany,
You are most welcome! Let me know if you have any other questions.
-Dr. Brad
thanks Dr.Brad @I hope to make more videos.You help us so much in examinations
Hi Alejandra,
Your answer will have the units of %g/ml. You are starting off with 2,250mg/L. You have to change mg to g, L to mL, and add the percent sign. 2,250mg/L (1 g/1000 mg) (1L/1000 mL) (100%) = 0.225% g/mL (or 0.225% w/v)
See how the conversion factor of 1g/1000mg changes the 2,250 mg to g? The conv factof 1L/1000 mL) changes the L to mL. Multiplying by 100% adds the % sign. Always start by writing down the units of the answer then figure out how to change the units of your given.
You are a very good instructor dr.brad;)
very helpful sir.
عاشت ايدك دكتور خوش تشرح ❤
Also, you can download my handout book and some exercises that might help.
Where I can find your book, please? you give very informatively explanation
Thanks a lot for your knowledge sir 🙏
Excellent 👍👍
Thank you so much Dr. Brad!
You are most welcome. Let me know if you have any other questions. Remember, the units will guide you through any problems that involve conversions, dosage calculations, percentages, percent strength, ratio strength, or drip rates.
Ok how about how much silver nitrate ( in grams) must be used in preparing 600mL of a solution such that 20 mL diluted to 1L will yield a 1:5000 solution.
Also, there is no need in this problem to convert the 50mg/5ml to percent strength.
THANK YOU SIR YOU SAVED MY LIFE
Karl Edward'butyuiioP Pena Glad I could help!
Nice👍
V/V questions seem to have been left out here, (because of their ease?) 500mL 50% betadine solution using normal saline _______ mL stock betadine; _______ mL normal saline. IS the answer simply 250mL of each? Or does the 0.9% for normal saline come into play?
Thank you!
Thank you for the videos
Thank you
very helpfull
Also, do you have any videos of you working test like questions? My pharmaceutical calculations teacher is really putting it on our class to say the least ha
Thanks for posting doc ...Help pls . How much oil do I need to add in a 30g of green tea to get 15% strength? Thank you ....
It would be 30 g in 200 mL total final product. I don't know if the tea would take up any volume.
@@BradWojcikPharmD thank you so much doc...
Dr. Brad, I have a question.
1. What is the initial strength of a solution that is made by adding 200 mL of purified water to make 600mL of a 25% solution?
+Nikki Jackson Hi Nikki. First calculate how many grams of active ingredient you have in the 600 mL of 25% solution. 600 mL(25g/100 mL)=150 g. So you started off with 150g/400 mL. Now just change that to a percent by multiplying by 100%. (150g/400mL)(100%)=37.5% w/v
Brad Wojcik hi I'm confused, where did the 400 come from?
In the question we are adding 200 mL of purified water to a solution to make 600 mL of 25%, so we must have started with 400 mL in the original solution.
Nice
hello,
I need help with this question I am stuck on ,
Threre are 2, 250 mg of NaCl in a L of a solution. What is the strength of the solution as a percent?
Thanks Igan!
This is an edited comment which is actually replacing my original post because I was wrong.
Brad's presentation shows and explains the topic extremely well.
Hi M Stephens.Thank for your comment.I know someone probably taught you to change a number to a percent by multiplying by 100, but if you multiply anything by 100, you are increasing its value by 100 times. So, (0.25)(100) = 25, not 25%. Whenever we convert units, we always multiply by a form of 1. For example, to convert 45 mg to g, we would multiply by (1 g/1000 mg) = 0.045 g. 1 g/1000 mg = 1 The same can be said about converting a number to a percentage. We want to multiply by a form of 1 so we don't change its value. 100% is 100/100, which is equal to 1. 0.25 (100/100) = 25/100= 25%.
I hope this clears up any confusion.
Dr. Brad
I think we both agree that 0.25 = 25%. Let's work backwards and find that value that we would multiply 0.25 by to get 25%. We will let x equal that value.
0.25 (x) = 25%. Solving for x we divide both sides by 0.25. 0.25(x)/0.25 = 25%/0.25 x = 100%. I would hope you keep an open mind and consider the fact that I may be right for the sake of your students.
M Stephens, Dr. Brad is also an instructor. There is no need to insult! He is absolutely correct in saying that you multiply by 100%. You include the percent so that it carries over into the answer! if you multiply a number by 100, then you just get a new number!! if you multiply by 100%, then you get a percent for an answer. Just look at your example! Your answer is wrong. 0.25 x 100= 25, not 25%.
Brad Wojcik Brad...I definitely have an open mind and, openly admit it when I make a mistake in class and out. Maybe we're not understanding one another. What I was saying was this: Let's say we have the fraction 1/4. To convert that into a decimal, it is 1 divided by 4 which equals 0.25 -- To convert 0.25 into a percent, we multiply it by 100 or move the decimal point two spaces right which gives us 25%, correct? Just as the ratio of 1:4 = 1/4, a 1:4 ratio = 25%. If a student gets 1 out of 4 questions right on a test, the student's score would be 25%...Do you agree or am I misinterpreting what you're saying?
Thanks, Brad.
Christina Sanchez Yes, Christina..... 0.25 x 100 DOES = 25.
Let's say you have 25% of a 4 fl.oz (120 mL) bottle of a suspension. That would mean you have 1 fl.oz (30 mL). But if we have 100% of a 4 fl.oz bottle of a liquid, we have 4 fl.oz or 100% of the 4 fl. oz of liquid....the same as multiplying by 1. Correct?
Also, my apology if I came off a rude. I was tired and irritable when I posted that yesterday! I'm sure Brad DOES know his material. I think we may be misunderstanding each other.
Thanks,
Mike
How about with the following : How many mL of a 3% w/v will be needed to make 60 ounces of a 1:200 (1 to 200) solution?
Thank you in advance
I think the easiest way is to calculate the weigh of active ingredient needed to make the 60 oz first. 60 oz (1 g/200 mL) (30 mL/oz) =9 g. Now calculate volume of 3% needed. 9 g (100 mL /3 g) =300 mL.
Thanks sir
How did u arrive to 100mg even though the answer jumps up at you because of the easy numbers. Can you show me what did u multiply and what did u divide? Je je The process is not quite clear to me. Thank you for your hep.
Hi Angela. Sorry, I was volunteering in Yosemite for a month and didn't have any internet. The units all canceled out except mg, so you multiplied 100 by 1, then divided by 1000, then multiplied by 1000 and divided by 1 to end up with 100 mg.
A physician prescribed an antibiotic to be mixed in white petrolatum to produce a 25% antibiotic preparation. The physician later changed the protocol to be only 12.5%. How much white petrolatum must be mixed with each 6 oz ointment container of 25% preparation to make the new 12.5% preparation? Calculate your answer in grams. This is a work book question but really doesnt make since. Can you help
Well, since 12.5% is half of 25%, you would add 6 oz of white petrolatum. If you are using 30 g per ounce it would be 180 g.
@@BradWojcikPharmD , ok I understand that but where did you come up with the 30. Can you write it with formula
Please email me at brad.wojcik@gmail.com so I can show you how it is done.
@@BradWojcikPharmD , I did email you I hope you received it
@@pammidkiff1893 HI Pam. No I didn't get it. Can you try again. Brad.wojcik@gmail.com
Thanks
Top
Hello I'm a little confused here. Im going to take my test soon and I want to make sure I know EVERYTHING. Lol please help me understand.
How can I find the ratio strength of a 20ml solution that contains 200mcg of a drug? Is it simple or am I thinking way into it?
Hi Emily. Thanks for the question. The ratio strength format is 1:another number, where another number is the amount of final product. In this case it is 1 g: mL of final product. What you have to start is 200 mcg:20 mL, but that is not the correct format. Start by changing 200 mcg to g. 200 mcg (1 g/1,000,000 mcg) = 0.0002 g. Now you can use either dimensional analysis or ratio proportion to find the number of mL which will contain 1 g. 200 mcg/20 mL = 1 g /x mL. Solving for x we get 100,000. So the answer is 1:100,000. Hope this helps!
-Brad
Also, I hope you downloaded a free copy of my book. Here is the link: payhip.com/b/5xVY
thank uou very much sir
sorry to bother you l have another word problem. the technician needs to prepare 2L of 0.25% acetic acid irrigation solution. the stock concentration of acetic acid is 25%. how many milliliters of sterile water have to be added?
+Ana Angel Hi Ana. It is never a bother to help students. You can do this a couple of different ways. You can use the formula V1C1=V2C2, where V1 is volume of the first solution, C1 is concentration of the first solution, V2 &C2 are volume and concentration of the second solution. We will say V1 &C1 are the 25% solution and V2C2 are the 2 L. We will change 2L to 2000 mL before we start. V1(25%)=(2000 mL)(0.25%) Solving for V1 we get (2000 mL)(0.25%)/25% = 20 mL, so you start with 20 mL of 25% and add 1980 mL of sterile water. The other way, without a formula, is to calculate how many grams of acetic acid are in the 2 L, then calculate how many mL of the 25% you need to get those grams. We will change 0.25% to 0.25g/100 mL (watch the % video if you didn't know that). 2000 mL(0.25g/100mL)= 5g. Now calculate how much 25% solution you need to get 5 g. 5 g(100 mL/25 g)= 20 mL. Hope this helps.
thank u so much🥹💗
You are welcome!
Where my gym bros at?? 👇
I am in real need of help on one, just not getting it. How many ml of 50 mg. per ml. of Rocephin equals 1.5 gm.
Hi Barb,
This problem is similar to about 80% of the problems you will encounter in pharmacy math. It has three parts. 1) the units of the answer (mL), the given (1.5 g) and one or more ratios ( 50mg/mL and 1000mg/g)). Write down the units of the answer and the given with an = between them. 1.5 g = mL. Now arrange the ratios so that g gets canceled out and you end up with mL.
1.5 g ( 1000 mg/g)( 1 mL/50 mg) = 30 mL.
It takes a little practice, but once you get the hang of it, these problems are very easy.Hope this helps. (p.s. Use g not gm)
Dr. Brad
Also note that all the ratios can be turned upside down if necessary. I like to call ratios like 50 mg/ mL a custom ratio because it is only good for this problem. For this problem 1 mL of the solution will equal 50 mg. So, 1mL/50mg equals 1, also 50mg/1mL equals 1. For 1000mg/g and 1 g/1000mg, these both equal 1 because 1 g = 1000 mg and anything divided by itself = 1. So, what you are doing is multiplying 1.5 g by 1 twice to change the appearance. Ratios like 1000 mg/1 g I like to call off the shelf ratios because you can use them anytime they fit the problem and they always = 1. I hope this makes sense.
Yes I am getting it now, thank you so much.
You're welcome. Let me know if you have any questions.
Also, you can download my book on the main channel page.
Yes l did the last answer and l got 20ml but where does it come from 1980?
+Ana Angel It asked how many mL of sterile water had to be added to get the 2000 mL. You started with 20 mL of the 25% and had to add another 1980 mL of sterile water to get the 2000 mL.
Wow
WARNING:
NO...to convert 0.45 to a percent, you multiply by 100 --NOT 100%.
For those confused, the first 5 minutes of this video may confuse you more!
Hi Msk7046. Thank for your comment.I know someone probably taught you to change a number to a percent by multiplying by 100, but if you multiply anything by 100, you are increasing its value by 100 times. So, (0.45)(100) = 45, not 45%. Whenever we convert units, we always multiply by a form of 1. For example, to convert 45 mg to g, we would multiply by (1 g/1000 mg) = 0.045 g. 1 g/1000 mg = 1 The same can be said about converting a number to a percentage. We want to multiply by a form of 1 so we don't change its value. 100% is 100/100, which is equal to 1. 0.45 (100/100) = 45/100= 45%.
I hope this clears up any confusion.
Dr. Brad
Brad Wojcik Another way of thinking about this is asking yourself what you would multiply 0.45 to change it to 45%. You would set up the equation: 0.45x=45%. Solving for x you would divide both sides of the equation by 0.45. 0.45x/0.45 = 45%/0.45. x = 100%
I hope this helps.
-Dr. Brad
MSK7046, you are wrong! if you want convert any number to a percent you multiply by 100%!! The key is to have the percent sign so that it carries over to the number you are converting to a percent. If you do not include the percent, you just have a number multiplied by 100. Having the % sign converts your number. Same with converting a percent to a decimal, you divide the number by 100%, then the percent signs cancel out.
My first post did not take into account Brad's reasoning. My apology.
45% over 100% then you cancel out the percent signs. its thats simple.
I hope to understand this pharm Cal. Cause it 😢😢
11 yrs ago
Are u alive??
Yes!
oooo thank you l got it
idk if I am missing something or not but .25 x 100% is not 25%
Are you alive Dr
Yes
Lol, awkward ending
The ending is very confusing with his ratio brackets, he didn't explain how to change grams into mg very well, it wasn't clear...very dangerous system with Epinephrine , better off avoiding it and find a easier way...don't want to make a mistake..LOL...But thanks anyways
Hi Sassy. Thanks for the feedback. The introduction video goes into detail on changing grams into mg using the ratio of 1000 mg/g and cancelling out the grams. I suppose I should have explained it again here for those who didn't watch the introduction video. Also, I did say in the video that it was better to use the mg/mL strength printed on the label of the epinephrine rather than the ratio strength.
Thank you
Thank you
You are welcome!