Question

An urn contains white balls numbered 1 to 15 and black balls also numbered 1 to 15. Suppose you draw 4 balls. What is the probability that (b) you get exactly one pair with the same number? (c) you get two pair with the same numbers?

Answer 1

First of all, what the total number of ways to draw the four balls?

Answer 2

b shouldn't be that hard

Answer 3

c is easier.

Answer 4

yeah i'll do c
(15C2) / (30C4)

:DD

Answer 5

got b yet?

Answer 6

b) C(15,1) C(14,2) C(2,2) (2*2) / (30C4)