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

`=.^6C_3.^5C_3.^5C_3`
`= (6!)/(3!3!)*(5!)/(3!2!)*(5!)/(3!2!)`
`= (6*5*4)/(3*2*1)*(5*4)/2*(5*4)/2`
`= 5*20*20 = 2000`
Answer