A box contains 12 marbles of three different colours green, yellow and blue---4 each.
If you were to close your eyes and pick them at random, how many marbles must you take out to be sure that there are at least two of one colour among the marbles picked out?
Pick:
A) 1
B) 4
C) 6
D) 3
E) 7
B   4   In the first three pickings you may get 1 of each colour, on the 4th pick there will be at least two of one colour.   Therefore, the answer is 4.
<result>B</result>
A box contains 12 marbles of three different colours green, yellow and blue---4 each.
If you were to close your eyes and pick them at random, how many marbles must you take out to be sure that there are at least two of one colour among the marbles picked out?