Answer to Question #225388 in Discrete Mathematics for asha

Question

A boy has 10 red balls, 20 blue balls,25 black balls ,and 30 pink balls .He select ball at random without looking at them .calculate the minimum number of balls he must select to be sure that at least 6 balls of the same color .

Answer 1

Suppose that a boy select 5red balls, 5 blue balls, 5 black balls, and 5 pink balls. Then if he selects the next, twenty first ball, he will have 6 balls of the same color.

$$5+5+5+5+1=21$$

The minimum number of balls he must select to be sure that at least 6 balls of the same color is 21.