A box contains 3 blue marbles, 4 red, 6 green marbles and 2 yellow marbles. If three marbles are picked at random, what is the probability that they are all blue?
Correct answer: A. 1/455
- A. 1/455
- B. 2/455
- C. 1/91
- D. 4/455
Explanation
All three must be selected from the 3 blue marbles, giving C(3,3) = 1 favorable selection. The total number of three-marble selections is C(15,3) = 455, so the probability is 1/455. The likely mistake is 1/91, which uses an incorrect total number of selections.
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