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2016/17 AHSMC Part 1 Problem 11

Problem 11 of 16

A box contains two red balls, two green balls and two yellow balls. If you randomly remove three balls from the box without replacement, what is the probability that you have removed one of each colour?

Answer choices

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Solution

There are a total of (63)=20\dbinom{6}{3} = 20 possibilities and only 88 are favourable. The requested probability is 820=25\dfrac{8}{20} = \dfrac{2}{5}. The answer is (B).

University of Alberta