Question

3.2

There are 5 green 7 red balls. Two balls are selected one by one without replacement. Find
the probability that first is green and second is red.
a

Answer 1

35/132.

Explanation:

There are a total of 12 balls. So:

Prob(First is green) = 5/12.

After the first selection there are 11 balls left.

Prob(The second is red) = 7/11.

The required probability = 5/12 * 7/11

= 35/132.

Note: the probabilities are multiplied because the 2 events are independent.