permutation combinations and counting principle

It would take a while to explain, but it is 588. Tell every to look at the question "i fun fact". You look at it as well.

for black:

tkhan:

In how many ways can three black

and

tkhan:

a box contains 12 black

that's 3 out of 12.

do you already know nCr (from n choose r)? nCr = n! / r!*(n-r)!
[input]n=12; r=3; n! / (r!*(n-r)!)[/input]
[input]ncr( 12, 3)[/input]

for green:

tkhan:

two green be picked

and

tkhan:

and 8 green marbles

that's 2 out of 8.
[input]ncr( 8, 2)[/input]

combinations combined (multiplied):
[input]ncr( 12, 3) * ncr( 8, 2)[/input]