Question

A bag contains 3 red, 5 black and 5 blue marbles. Four marbles are selected at random without replacement:
- the probability that all 4 are black?
-the probability that exactly two are blue and none are red?

Answer 1

2/5

Answer 2

First black marble = 5/13, second = 4/12, third = 3/11, fourth = 2/10.

The probability of all events occurring is found by multiplying the individual probabilities.

First blue = 5/13, second = 4/12, first non-red = 8/11, second non-red = 7/10.

The probability of all events occurring is found by multiplying the individual probabilities.