Question

In how many ways can a gymnastics team of 4 be chosen from 9 gymnasts?

Answer 1

dont get this one, could someone show me the steps?

Answer 2

"chosen" so you use combinations

Answer 3

from 9 choose 4.
9C4 = ...

Answer 4

arent you missing something?

Answer 5

362880?

Answer 6

that's 9!

Answer 7

don't forget to divide by all the same combinations (n-r)!

Answer 8

\[9C4 \implies \frac{9!}{4!(9-4)!}\]

Answer 9

dividing by (n-r)! is what separates the combination formula from the permutation, because you are not counting all the different arrangements

Answer 10

isnt dividing r! what separates it?

Answer 11

\[nCr = \frac{n!}{r!(n-r)!}\]
\[nPr = \frac{n!}{(n-r)!}\]

Answer 12

dividing by r! is just the difference i see =))

Answer 13

126!!

Answer 14

i hope those ! arent factorials :p haha

Answer 15

anyway yeah. 9C4 = 126

Answer 16

ya:P

Answer 17

Ooops, I meant r! not (n-r)! for all the above posts. Sorry :o