IBPS RRB Office Assistant 21 Sep 2014 Paper

(1) Total number of balls in the bag = 4 + 6 + 5 = 15
Total possible outcomes = selection of 3 balls out of 15 balls
=15C3=

15×14×13

1×2×3

=455
Favourable outcomes = selection of 3 balls out of 9 balls(except orange balls)
=9C3=

9×8×7

1×2×3

=84