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Combinations Videos 11 videos

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Permutations and Combinations 2384 Views


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00:00

Thank you We sneak Permutations and combinations are la shmoop

00:08

If you've ever considered the consequences of your actions while

00:11

you're probably interested in the concept of possible outcomes especially

00:15

ever since you tried sneaking past that no trespassing sign

00:18

outside the willoughby place you had better ideas today Oh

00:24

Me there are a couple of different methods We used

00:26

to count outcomes depending on whether or not the order

00:29

of what we're counting on matters For example if you

00:32

want to know how many different ways there are to

00:34

arrange any three of those seven blouses you just shoplifted

00:38

right As soon as one is in place in your

00:42

closet you'll have one fewer options for the next life

00:46

So order definitely matters or something like this would use

00:50

permutations for the permutation formulas Written is n p k

00:55

which is used to express the number of possible permutations

00:58

of k objects from a set of any It can

01:03

also be written in factorial over the quantity and minus

01:07

k factorial This In the case of the blouses are

01:14

in his seven number of blouses In our case three

01:17

the number of glasses we want teo organized no playing

01:21

into our formula We'd have seven factorial over the quantity

01:24

seven minus three factorial or seven times six times five

01:28

times four times three times two times one over four

01:31

times three times two times one Well the four three

01:33

two one all cancel leaving seven times extent five or

01:36

two hundred ten possible permutations of three blouses hoping this

01:43

party But what about when order doesn't matter Like what

01:47

If you want to sell two of those dresses on

01:49

the black market blouse market and you're deciding which due

01:53

to take up the hangars well here the order of

01:56

the two doesn't matter It's just a question of how

01:58

many combinations of to you even select well we've got

02:01

a formula for this one too and see our or

02:05

in factorial over our factorial times the quantity and minus

02:10

are factorial Where it's our objects from a set of

02:14

an object r all right well we can plug again

02:19

replacing end with seven and are with two to get

02:22

seven factorial over To factorial times The quantity Seven minus

02:27

two factorial or seven times six sometimes four times three

02:31

times two times one i think all over two times

02:34

one times five times four times three times two times

02:38

one part We can start by canceling everything from the

02:40

five on down the line here which leaves us with

02:43

just seven times six over two times one which is

02:47

forty two over two or twenty one twenty one combinations

02:50

of two dresses you could try hock it on the

02:52

street are always get even Just remember permutations went Order

02:57

matters combinations When it doesn't That way you'll have plenty

03:01

of time time all these over while you're serving your

03:03

sentence in youth detention center Because shoplifting glasses is not 00:03:07.51 --> [endTime] way not good

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