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Problem 6 - Entrance Test

A bag contains 3 red and 5 blue marbles. Three marbles are drawn without replacement. What is the probability that exactly two are blue?

Correct: C

Total ways C(8,3)=56. Favorable: choose 2 blue from 5 and 1 red from 3: C(5,2)·C(3,1)=10·3=30. Probability=30/56=15/28.