A box containing 20 yellow balls, 9 red balls and 6 blue balls. If the balls are selected at random, what is the smallest number of balls that need to be selected so you will select at least two balls of each colour

Answer 1

probability - wise, the easiest pair to pick would be the yellow pair.

best case scenario:
you have picked 1 yellow, 9 reds and 6 blue.
So you definitely have a pair of blues , a pair of reds but no pair of yellows.
you have picked 16 balls.
So the 17st pick would have to be a yellow.

So minimum is 17