Question

A bag contains 20 yellow balls, 23 green balls ,27 white balls. How many minimum balls one should pick out so that to make sure he gets at least 2 balla of all colours

Answer 1

he should pick 6 ball totally.

Here is your solution,

suppose he picks 5 balls of all different colours then when he picks up the sixth one, it must match any on of the previously drawn ball colour.

thus he must pick 6 balls.