Find the conditional probability of the indicated event when

Find the conditional probability of the indicated event when two fair dice (one red and one green) are rolled. HINT [See Example 1.] The red one is 5, given that the sum is 11.

Solution

There are only 2 ways to produce a sum of 11, that is:

{R = 5, G = 6} or {R = 6, G = 5}

Thus,

As one of these results have R = 5 (red one is 5), then

P(red is 5|sum is 11) = 1/2 or 0.5 [ANSWER]