Question

Evaluate 15C2 and 15P2

Answer 1

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

Answer 2

15!/2!(15-3)!

Answer 3

almost
try that one again.

Answer 4

15!/2!(15-2)!

Answer 5

hello?

Answer 6

is anyone gonna help

Answer 7

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

Answer 8

15!2(15-2)!

Answer 9

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

Answer 10

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

Answer 11

15/(15-2)

Answer 12

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

Answer 13

ok

Answer 14

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

Answer 15

remember this one:

Answer 16

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

Answer 17

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

Answer 18

let me know if that makes sense

Answer 19

so we do 15 times 14 times 13?

Answer 20

correct

Answer 21

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

Answer 22

and thats the answer to the first one?

Answer 23

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

Answer 24

2730

Answer 25

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

Answer 26

but thats not the answer

Answer 27

what did you get?

Answer 28

2730

Answer 29

on the top

Answer 30

after you cancel you should only have 15*14 left

Answer 31

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

Answer 32

210

Answer 33

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

Answer 34

it was 105 u made me mess up

Answer 35

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

Answer 36

u never told me that

Answer 37

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

Answer 38

now what about the permutation one?

Answer 39

i am gonna post a new one now

Answer 40

because u made me get it wrong

Answer 41

okay...good luck