Question 117442
Although it is a small possibility, you could draw all 8 red marbles to begin with. Then you
could draw all 7 blue marbles. This means that you have removed 15 marbles and still don't 
have a white one. However, the next three draws would only be white, so you would be done.
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Therefore, you need to draw 18 of the 20 marbles to be absolutely sure that you had three
marbles of each color.
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Hope this helps you to understand the problem.
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