I love how he explains where the formulas came from....it's a lot more interesting understanding how that happened than just memorizing a series if seemingly random facts!
wowWOW you are a much better teacher than the teacher that teaches my combinations and permutations class. she spent 45 minutes writing on the blackboard and explaining it, and not a single one of us left that class understanding combinations. Dr renegar, if you are reading this, please don't grade me down for posting it.
A bunch of people are really confused by this, as I can see in the comments. For permutations, all you have to do is take the numbers in the problem and multiply them. For example, If there is 10 numbers on a lock and you have to use three of them, count down from ten three times. 10,9,8 Then you multiply these together. 10x9x8=720 So there is 720 combinations of numbers. I hope this helps, it kind of explains it easier than in the last video (no offense, your videos are great)!
Maddie Ricke Im really glad u stepped forward yourself to explain it and help the confused people like me out but umm in case of a password u can never have a case where u can't repeat a digit ANYWAYS those r specific conditions of different qns. Good job! 👍🏼😋
Hey people if you find this video confusing to understand properly then you can check another video of them which is titled as "Combination intro". Believe me guys that's just super helpful and simple.
how is this guy so much better than my teacher? i paid like a hundred dollar in school so i can learn including this and nothing happened then i searched this on youtube and didnt spent any and this is so much clearer like wtf?
+Khan Academy Thank you so much for these videos! I am currently studying for the GRE and your explanations are very helpful and easy to follow! Please keep up the amazing work, sir!
How I understand now is, you need to consider those 6 combinations as essentially 1 type bcoz the order doesn't matter, so to do the same for all letters you divide the entire permutation by 6...because the permutation (upper part) contains all combinations..
Maybe I'm too late, but I'll reply anyway (maybe that will help other people too): as Sal said, "a combination is a permutation where you don't care about the order". So, in short, you'll use permutations when order matters and you'll use combinations when it doesn't. :)
Our Lord JESUS CHRIST is the Light of the world. Whoever follows Him will never walk in darkness, but will have the light of life. Follow Jesus and you will be saved !
@Awzyn8 no. Order matters is generally considered to mean that you take order into account. You use permutations when you take order into account (that is, B and then A is not the same as A and then B)
My textbook gives out this information but in a much complicated way. Thanks for making me understand this easily by practical application and explaining the derivation.👍
honestly, i did find it confusing, i think it is helpful in any videos to stop and pause and think about it. clarify what you don't understand and write them down if you have to. then go back watching the video looking the answers to the specific questions you have written down.
Perhaps it is the fact that he doesn't usually call his explanations proofs that makes them so straightforward? Perhaps hearing the word proof automatically triggers a sense fear that makes it so hard sometimes to grasp the concepts from others. Or simply put too many are just not natural teachers. But Khan may have been made for this! I just he's appreciated enough, even if I'm sure that probably wouldn't matter to him one way or another! I'm simply not sure there are too many like him!
Omg I get it!!!!! between Permutation and Combination, my stupid text teach it the other way around, but I think it makes sense to teach Permutation before Combination.
permutation VS combination difference? example:" there are many combinations to select from but only one permutation will unlock the lock." correct me if i'm wrong.
can anyone help me with this question? what is the chance that 7 children in the same family are born on 7 different days in the week? A: 1/7 B: 2/7 C: 5!/7^5 D: 6!/7^6 the answer is D, but I don't know why, can someone please help me?
Can some please help me clarify the difference between these 2? 13C2 and (13C1 x 12C1) Explain it in words please not algebraically. Because I'm trying to understand the "story" behind it. :/ or provide an analogy or of sort. Thanks ! :)
13c1 x 13c2 is equal to 13 x 12, this is different to 13c2 because 13c2 makes sure you don't get the same thing but in a different order. But with 13c1 x 13c2 you could have the same two things arranged in different ways
No... I don't understand why this comment got upvoted. That's not how it works at all lol. The position of something does not matter in a combination. What matters is whether or not it was present. If i have a red, blue, and orange ball and I'm trying to pick 2 at random, I might pick red and orange, or orange and red. If this was a permutation, red orange and orange red would be two different things. However, in a combination, red orange is the exact same thing as orange red. A combination looks at the end result, not the order of which it was chosen.
Mr. Stephen, you're also correct :) But you just flipped the other side of the coin. I just showed the very basic of these two. To elaborate more clearly, here's my example: Suppose we want to select two out of three boys A, B, C. Then, possible selections are AB, BC and CA. Note: AB and BA represent the same selection. AB and BA are two different permutations but they represent the same combination.
+Chen Bai In means sometimes,in real life, order matters; sometimes not. That is how you treat 2 variations: A,B,C or B,C,A. Are these 2 variations of equal importance to you? Well,sometimes yes,other times not: Let's say A,B,C are chairs in the kitchen on which 3 people may sit. Here 3 chairs are enough for 3 people and it doesn't really matter who sits on which chair. Other example is where you want to open your locker: Let's say you forgot/lost the combination of the locker and you ask your wife:: Do you remember the numbers of the locker? She answers: Wait a little,the numbers are...... 23-41-16-53-11-63-41 But you have to run the right order. So you ask: Is this the right order?
+Chen Bai think of it as how many different groups can you make from x amount of people, like let's say you have 6 people and you want to make teams. well, you could have team ABC, but there's no point in making a team BCA right?
A mother with 7 children takes three at a time to a cinema. She goes with every group of three that she can form. How many times can she go to the cinema with distinct groups of three children? Why can't we solve this using this approach i assume that there are 7 digits from which i have to form 3 digits which must not be repetitive in nature so there can be 7*6*5 different ways....where am i making mistake could you please help me understand that
Help. Can anyone answer this, please?: There are 100 marbles in a jar-each one is unique in colour, they're translucent and you can see that they have shape designed inside in the middle. I have to pick the "Lucky 5" of them w/c are: Blue Star; Green Leaf; Red Pentacle; Yellow Butterfly; and White Guitar I'm blindfolded and am given the chance to pick 20 marbles. What's my chance (in %) of getting the Lucky 5? TIA
sure, sure. i'm not native english speaker, so i may have some trouble defining things. you see, the first you go catch a marble, you have 5% chance of getting one of the ''lucky 5'' and 95% of not getting one of them. so, first, i will calculate the chance of not gettinn any of the lucky five, than, i just have to take that number and descrease it from 1. The answer i said above is wrong. but i think i know the right, now. so: first, you have 95/100 chance of not getting one of the lucky 5 marbles. the next marble will be 94/99, then 93/98 an so forth until 75/80. you take all those numbers (95/100 times 94/99 times.... 75/80) and decrease from 1 (which would be 100%) and you will get the chance of getting all of the lucky 5 marble... sorry if i confused you.. and i maybe even be wrong :(
Why is he using P for combinations? Isn't he suppose to be using C because the answer needs to be divided by the ! of the number on the right of the C?
hello sal ! can you please tell me how to solve lock system which take three digit code from 0 to 9 so how many possible combination it will be ? as i think combination should start from 000-999 so there should be 999 combination but when im solving its136.6 so i think some where im wrong so please correct me
if we care about the order its 10P10, which means10!/(10-10)!=10!/0!=10!/1....and you do the math. but if we dont care about the order will be like this:10!/(10!(10-10)!=10!/0!=10!/10! =1..just take in consideration that 0! =1..i hope that was helpful :)
hello prof thanks a lot for your vids. ahmm can I ask for your YM so that I can consult you if we have new math problems or lessons pls, its ok if you cant I totally respect your privacy Man.
![PASULOL รามเกียรติ์ ตอนที่ 4 นนทกพบรัก [Ramakien Ep.4: Nonthok in love]](http://i.ytimg.com/vi/tMUQgmZzf_A/mqdefault.jpg)
I think that's the best way I've ever had combinations explained to me. That formula makes sense now.
I love how he explains where the formulas came from....it's a lot more interesting understanding how that happened than just memorizing a series if seemingly random facts!
wowWOW you are a much better teacher than the teacher that teaches my combinations and permutations class. she spent 45 minutes writing on the blackboard and explaining it, and not a single one of us left that class understanding combinations. Dr renegar, if you are reading this, please don't grade me down for posting it.
sal is the best teacher on earth. even my dad learns a few things! i am in grd 8 and can do calculus thanks to sal!
A bunch of people are really confused by this, as I can see in the comments.
For permutations, all you have to do is take the numbers in the problem and multiply them.
For example,
If there is 10 numbers on a lock and you have to use three of them, count down from ten three times.
10,9,8
Then you multiply these together.
10x9x8=720
So there is 720 combinations of numbers.
I hope this helps, it kind of explains it easier than in the last video (no offense, your videos are great)!
Except in your example you can't resuse the same number, in case anyone gets confused.
Maddie Ricke Im really glad u stepped forward yourself to explain it and help the confused people like me out but umm in case of a password u can never have a case where u can't repeat a digit ANYWAYS those r specific conditions of different qns. Good job! 👍🏼😋
Maddie Ricke that's permutation and not combination
THANK YOU
Thanks
Hey people if you find this video confusing to understand properly then you can check another video of them which is titled as "Combination intro".
Believe me guys that's just super helpful and simple.
Thanks for being there to explain things for me for free when my maths teacher really, reeeeally couldn’t. :) also tip: listen on 2x speed
how is this guy so much better than my teacher? i paid like a hundred dollar in school so i can learn including this and nothing happened then i searched this on youtube and didnt spent any and this is so much clearer like wtf?
dude Sal... you should win the Nobel Prize
I'm not even kidding
+Khan Academy Thank you so much for these videos! I am currently studying for the GRE and your explanations are very helpful and easy to follow! Please keep up the amazing work, sir!
How I understand now is, you need to consider those 6 combinations as essentially 1 type bcoz the order doesn't matter, so to do the same for all letters you divide the entire permutation by 6...because the permutation (upper part) contains all combinations..
This was better than how my Algebra 2 teacher explained it, this provided a much more enjoyable experience. :D
YOU ARE GREAT TEACHER!!!!!!! permutations and combinations became SOOOOOOOO Easy!
Can Khan Academy just come teach my class? You guys make so much more sense.
....... I am speechless... Not by seeing and understanding, rather by how confusing permutation and combination is... 😵😵😵
why cant khan academy just teach the world math. you guys are amazing!
Maybe I'm too late, but I'll reply anyway (maybe that will help other people too): as Sal said, "a combination is a permutation where you don't care about the order".
So, in short, you'll use permutations when order matters and you'll use combinations when it doesn't. :)
Our Lord JESUS CHRIST is the Light of the world. Whoever follows Him will never walk in darkness, but will have the light of life. Follow Jesus and you will be saved !
Thank you sir. This really helped me a lot because my teacher in MTG, didnt say the formula. This will help me on the quiz tomorrow.
@Awzyn8
no. Order matters is generally considered to mean that you take order into account. You use permutations when you take order into account (that is, B and then A is not the same as A and then B)
it made sense when you said in combinations that we divide the permutation by the times the r spots could be arranged
We really used to memorize the formulae but today I learned the concept behind it..
It was great!!
Thanks
My textbook gives out this information but in a much complicated way. Thanks for making me understand this easily by practical application and explaining the derivation.👍
Seriously, Khanacademy= WIN
Thank you for this video. My textbook gave some convoluted explanation and I was having a hard time comprehending!
One of the best explanations ever ❤️❤️
honestly, i did find it confusing, i think it is helpful in any videos to stop and pause and think about it. clarify what you don't understand and write them down if you have to. then go back watching the video looking the answers to the specific questions you have written down.
THANK GOD THIS MAKES SO MUCH MORE SENSE NOW
The division by r! is the number of ways the chairs may be rearranged under the successful players who got a seat in n-player, r-seat musical chairs.
Perhaps it is the fact that he doesn't usually call his explanations proofs that makes them so straightforward? Perhaps hearing the word proof automatically triggers a sense fear that makes it so hard sometimes to grasp the concepts from others. Or simply put too many are just not natural teachers. But Khan may have been made for this! I just he's appreciated enough, even if I'm sure that probably wouldn't matter to him one way or another! I'm simply not sure there are too many like him!
THANK YOU SO MUCH. you saved my math grade.
thank you, it helped me remember my precalculus stuff.
Do you remember this comment?
we can say combination is (5 & 3) can be like this ( 5.4.3 )/3!=10 its like the same for permutation p(5,3) = 5.4.3=60 you go down from 5 3 times;)
amazing how people still watch these. he should update them all. it's hard for me to see due to the low quality.
Thanks alot for the logic of these stuff its really useful.
It's great and makes sense so much. Thank you
The last 3 videos summed up a month of stats and probs courses
Your videos are Helpfull .. So that PLEASE Update them ..
best explanaition everrrrr!!! BEST
This guy is a boss.
Thank you so much, this video was extremely helpful!
love this channel
Yes you are indeed the man.
This helped me a lot!
This helped me a lot. They don't give you this information when studying for your GED. I'm not writing a chart for all that shit! hahahaha
Omg I get it!!!!! between Permutation and Combination, my stupid text teach it the other way around, but I think it makes sense to teach Permutation before Combination.
Ur video is really good but I'm still a bit confused. it would be awesome if you could do some more examples.
Yet it looks so easy..
permutation VS combination difference?
example:" there are many combinations to select from but only one permutation will unlock the lock."
correct me if i'm wrong.
Nice video on permutations
I came here to know how many combinations there were for a 4 number combinations and why and I got bombed with all this
could u please make a playlist for all the P&C videos, in order? thanks
permution-> i care about the order of numbers
combination--> i dont care about the order of numbers.
This is the only video I don't understand from Khan academy... pls pls I need help
Because its mostly permutations and little of combos, as user EpicMinecreafSkills has stated.
Combinations part starts from 2:30
Could you make a selection where you review data management.
Even though this is the combinations video, he spent the first 4 and a half minutes explaining permutations! Why?
+EpicMinecraftSkills to piss you off, of course lol
Hmmm... makes sense.
because you need to know permutations first
You obviously didn't pay much attention during this video. The formula for combination involves permutations' formula
thank you!! now I understand it.
can anyone help me with this question?
what is the chance that 7 children in the same family are born on 7 different days in the week?
A: 1/7
B: 2/7
C: 5!/7^5
D: 6!/7^6
the answer is D, but I don't know why, can someone please help me?
Does it mean the following:
Number of combinations = (Total number of permutations) / (Number of permutations per combination)
Can some please help me clarify the difference between these 2?
13C2
and
(13C1 x 12C1)
Explain it in words please not algebraically. Because I'm trying to understand the "story" behind it. :/ or provide an analogy or of sort. Thanks ! :)
13c1 x 13c2 is equal to 13 x 12, this is different to 13c2 because 13c2 makes sure you don't get the same thing but in a different order. But with 13c1 x 13c2 you could have the same two things arranged in different ways
So in other words,
Permutation: ORDER MATTER
(A,B,C)
(B,C,A)
(C,A,B)
Combination: POSITION MATTER
(A) ( ) ( ) (B) ( ) ( ) (C) ( ) ( )
( ) (A) ( ) ( ) (B) ( ) ( ) (C) ( )
( ) ( ) (A) ( ) ( ) (B) ( ) ( ) (C)
No... I don't understand why this comment got upvoted. That's not how it works at all lol. The position of something does not matter in a combination. What matters is whether or not it was present. If i have a red, blue, and orange ball and I'm trying to pick 2 at random, I might pick red and orange, or orange and red. If this was a permutation, red orange and orange red would be two different things. However, in a combination, red orange is the exact same thing as orange red. A combination looks at the end result, not the order of which it was chosen.
Mr. Stephen, you're also correct :) But you just flipped the other side of the coin. I just showed the very basic of these two. To elaborate more clearly, here's my example:
Suppose we want to select two out of three boys A, B, C. Then, possible selections are AB, BC and CA.
Note: AB and BA represent the same selection.
AB and BA are two different permutations but they represent the same combination.
Terence Cruz Yup, perhaps i just misunderstood ur first explanation
Thank you, i totally get it now! :)
im in year 4 and i can understand this
What would a question ask for that would prompt you to use combinations over permutations. Like, how do you tell?
You're right, cuz this is a video.
I understand it!
I.. dont get it?
Awesome, thanks man!
all over the place
When we learned permutations and combinations, my teacher didn't include factorials. How do I find the different combinations without the factorials?
Your name is cream pied
Still don't understand it. What do you mean by " in order " "not in order"?
In permutation the order doesn't matter but in combination the order does matter.
+Annabella Partido the other way
+Chen Bai
In means sometimes,in real life, order matters; sometimes not.
That is how you treat 2 variations:
A,B,C or B,C,A.
Are these 2 variations of equal importance to you?
Well,sometimes yes,other times not:
Let's say A,B,C are chairs in the kitchen on which 3 people may sit.
Here 3 chairs are enough for 3 people and it doesn't really matter who sits on which chair.
Other example is where you want to open your locker: Let's say you forgot/lost the combination of the locker and you ask your wife::
Do you remember the numbers of the locker?
She answers: Wait a little,the numbers are...... 23-41-16-53-11-63-41
But you have to run the right order.
So you ask:
Is this the right order?
+Chen Bai think of it as how many different groups can you make from x amount of people, like let's say you have 6 people and you want to make teams. well,
you could have team ABC, but there's no point in making a team BCA right?
A mother with 7 children takes three at a time to a cinema. She goes with every group of three that she can form. How many times can she go to the cinema
with distinct groups of three children?
Why can't we solve this using this approach i assume that there are 7 digits from which i have to form 3 digits which must not be repetitive in nature so there can be 7*6*5 different ways....where am i making mistake could you please help me understand that
THANK YOUUUU
Because people aren't channels.
thank uu , ur a boss
Help. Can anyone answer this, please?:
There are 100 marbles in a jar-each one is unique in colour, they're translucent and you can see that they have shape designed inside in the middle. I have to pick the "Lucky 5" of them w/c are:
Blue Star;
Green Leaf;
Red Pentacle;
Yellow Butterfly; and
White Guitar
I'm blindfolded and am given the chance to pick 20 marbles. What's my chance (in %) of getting the Lucky 5?
TIA
1-(0,95)^20 thats your chance
Thanks but i kind of not understand the number 1-(0,95)^20 .pls explain? :(
sure, sure. i'm not native english speaker, so i may have some trouble defining things.
you see, the first you go catch a marble, you have 5% chance of getting one of the ''lucky 5'' and 95% of not getting one of them. so, first, i will calculate the chance of not gettinn any of the lucky five, than, i just have to take that number and descrease it from 1.
The answer i said above is wrong. but i think i know the right, now. so: first, you have 95/100 chance of not getting one of the lucky 5 marbles. the next marble will be 94/99, then 93/98 an so forth until 75/80. you take all those numbers (95/100 times 94/99 times.... 75/80) and decrease from 1 (which would be 100%) and you will get the chance of getting all of the lucky 5 marble... sorry if i confused you.. and i maybe even be wrong :(
Mau Lourencena thanks mau! It's diffucult but i get your point :)
i just made the calculations here, and it would be about 70%, if i'm not wrong
What's the formula of finding how many routes are in 20*20 grid ?
Why is he using P for combinations? Isn't he suppose to be using C because the answer needs to be divided by the ! of the number on the right of the C?
He takes so long to explain everything. I'll just read about it.
Confusing :(
uh...what?
this comment is Forever Alone
Not anymore. :)
hello sal ! can you please tell me how to solve lock system which take three digit code from 0 to 9 so how many possible combination it will be ? as i think combination should start from 000-999 so there should be 999 combination but when im solving its136.6 so i think some where im wrong so please correct me
Right?
I
i love your channel but this time it was so fast and couldn't get into subject.
still don't know when to use permutation or combination
+Swiftlaker what was that four vids.?
What if there were 10 people and 10 seats????what would be the possibilities
if we care about the order its 10P10, which means10!/(10-10)!=10!/0!=10!/1....and you do the math. but if we dont care about the order will be like this:10!/(10!(10-10)!=10!/0!=10!/10! =1..just take in consideration that 0! =1..i hope that was helpful :)
Thnx
Ashutosh Pani u r welcome, bro:)
this confused the hell out of me even more....
How else came here from the sudanese certificate exam ??
Extremely confusing for me.
Because people don't like to learn? Maybe :)
hello prof thanks a lot for your vids. ahmm can I ask for your YM so that I can consult you if we have new math problems or lessons pls, its ok if you cant I totally respect your privacy Man.
SAL THANK YOUUUUUUU
You write better on a computer, than i do with a pen and paper.
What the fuck
Did he redo this video?
honestly you should not have chose a subset, that just made it more confusing! assuming combination is not about subset.
I DONT GET WHEN YOU USE PERMUTATION VS COMBINATION ???
WHAT TYPE OF QUESTION