Posted by Isi on .
A bag contains 6 black balls,5 red balls and 4 white balls,if 3 are selected at random without replacement determine the probability that (1)all 3 are black (2)all 3 are red (3)2 are black and 1 white (4)at least 1 of each colour is selected.

Math 
PsyDAG,
The probability of all events occurring is found by multiplying the probabilities of each events. However, once a particular ball is picked, you have one less ball total and in that category. Because it is multiplication, it does not matter which ball is picked first. For example:
1. 6/15 * 5/14 * 4/14 = ?
From this you should be able to do the rest.