Question

Find the number of ways of selecting 9 balls from 6 red balls, 5 white balls and 5 blue balls if each selection consists of 3 balls of each colour.

Answer 1

Solution:
Three red balls can be selected out of 6 red balls in ⁶C₃ ways. Similarly, three white balls can be selected out of 6 white balls in ⁵C₃ ways. And three black balls can be selected out of 5 blue balls in ⁵C₃ ways. The number ways of selecting 9 balls = ⁶C₃ × ⁵C₃ × ⁵C₃

= 20*10*10

= 2000