SOLUTION: A box contains an equal number of red, blue and yellow marbles, all mixed up. What is the minimum number of marbles to be taken out blind folded (or without looking at the box) so

Question 657853: A box contains an equal number of red, blue and yellow marbles, all mixed up. What is the minimum number of marbles to be taken out blind folded (or without looking at the box) so that you can be sure of getting 3 marbles of the same colour?
(a) 3 (b) 5 (c) 7 (d) 9 (e) 11

Answer by kevwill(135) (Show Source): You can put this solution on YOUR website!
The answer is (c) 7.
In the worst case, you would pull two of each color with your first six draws. On the seventh draw, the color of the marble must match one of the colors for which you already have two marbles.

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