Evaluate 15C2 and 15P2

- anonymous

Evaluate 15C2 and 15P2

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- anonymous

well...we did a similar one earlier no? 15c2 you can do just like we did earlier...for 15p2 the formula is different...i'm sure your book has it...please look it up...if you can't find it i'll show you...but u need ot try to find it first

- anonymous

15!/2!(15-3)!

- anonymous

almost
try that one again.

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## More answers

- anonymous

15!/2!(15-2)!

- anonymous

hello?

- anonymous

is anyone gonna help

- anonymous

that one is good...now do the permutation one

- anonymous

15!2(15-2)!

- anonymous

have you found the formula for permutations? it's slightly different...but looks almost like combination

- anonymous

no...that's not it
permutation is n!/(n-r)!

- anonymous

15/(15-2)

- anonymous

yes...but don't forget the factorials!

- anonymous

ok

- anonymous

so u do 15 times 14 times 13 times 12 times 11 times 10 or?

- anonymous

remember this one:

##### 1 Attachment

- anonymous

the reason i wrote it like that is because i wanted the 10! on the top to cancel with the 10! on the bottom

- anonymous

but this time we don't have 10! on the bottom, instead we have 13!...write it like this:

- anonymous

##### 1 Attachment

- anonymous

let me know if that makes sense

- anonymous

so we do 15 times 14 times 13?

- anonymous

correct

- anonymous

try to be clever with the way you write it, so that you can cancel as much as possible...technically you can just multiply EVERYTHING. but that will give you HUGE numbers...better to cancel...so we make our lives easier

- anonymous

and thats the answer to the first one?

- anonymous

well, at least multiply it out...what do you get?

- anonymous

2730

- anonymous

after you cancel stuff...multiply and see what number you get

- anonymous

but thats not the answer

- anonymous

what did you get?

- anonymous

2730

- anonymous

on the top

- anonymous

after you cancel you should only have 15*14 left

- anonymous

cause the 13! cancelled with the 13! in the denominator

- anonymous

210

- anonymous

correct...and what's left on the bottom?

- anonymous

it was 105 u made me mess up

- anonymous

^_^ i did? ... well...it was 210 on the top and 2 on the bottom...so you have 210/2 = 105

- anonymous

u never told me that

- anonymous

...of course not...you have to find the answer yourself

- anonymous

now what about the permutation one?

- anonymous

i am gonna post a new one now

- anonymous

because u made me get it wrong

- anonymous

okay...good luck

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