Find the number of ways of selecting 9 balls from 6 red balls, 5 while balls and 4 blue balls if each selection consists of 3 balls of each colour.
Total number of red balls = 6
Total number of white balls = 5
Total number of blue balls = 4
No. of ways of selecting 3 balls which is red = 6C3
No. of ways of selecting 3 balls which is white = 5C3
No. of ways of selecting 3 balls which is blue = 4C3
Thus,by Multiplication principle, the total number of ways would be,
6C3 
5C3 
4C3
Applying formula, nCr = 
, we get
⇒800 ways
Thus, the number of ways of selecting 9 balls from 6 red balls, 5 while balls and 4 blue balls if each selection consists of 3 balls of each colour would be 800.
1