Question

A box contains 2 white marbles, 3 blue marbles, 7 black marbles and 9 green marbles. Juan takes one marble at time out of the box and without looking at its color puts it in another box. What is the least number of marbles Juan must transfer to the second box to be certain that two of the marbles in the second box are the same color?
Please explain??????

Answer 1

Since there are 4 colors, even if the 1st 4 marbles are all different, the 5th marble must be the same color as one of them.