If it rains ​tomorrow, the probability is 0.8 that John will practice his trombone. If it does not rain tomorrow, there is only a 0.4 chance that John will practice.

Question

If it rains ​tomorrow, the probability is 0.8 that John will practice his trombone. If it does not rain tomorrow, there is only a 0.4 chance that John will practice. Suppose the chance of rain tomorrow is 60​%. What is the probability that John will practice his trombone​?

Answer 1

Draw a tree diagram.

practice 0.8

rain

0.6 not practice 0.2

not rain practice 0.4

0.4

not practice 0.6

probability rain and practice = 0.6 * 0.8 = 0.48