DAY 238
Credit: Yvonne Parietti in Parade Magazine--Ask Marilyn--by Marilyn Vos Savant

Sat that a bag contains 100 marbles: 30 red, 30 blue, 30 green, plus a mix of 10 yellow and orange marbles. To be certain that you have 10 marbles of the same color, what is the minimum number you would need to remove (without looking) from the bag?

HINT: Consider the worst case.

Answer:

38...........In the unluckiest case, you would remove (in whatever order) 9 red marbles, 9 blue , 9 green, and all 10 of the yellow and orange marbles. So far, you have removed 37 marbles, but still do not have 10 of the same color. If you remove one more marble, it will be either red, blue, or green---giving you 10 of the same color.