Q. What is the probability of choosing a red ball?

Ans.

A box contains a red, blue and white ball. Two are drawn with replacement. (This means that one ball is selected, its color is observed, and then the ball is replaced in the box.) The balls are scrambled before the next one is chosen. Show the sample space using a tree diagram and a list. What is the probability of choosing a red ball?

Solution:

List: S = {(R, R), (R, B), (R, W), (B, R), (B, B), (B, W), (W, R), (W, B), (W, W)}
Notice: n(S) = 9

Let R represent the event of choosing a red ball.
R = {(R, R), (R, B), (R, W), (B, R), (W, R)}
n(R) = 5

The probability of choosing the red ball is