The weather forecaster indicates that there is a 25 chance o

The weather forecaster indicates that there is a 25% chance of rain on Saturday and a 25% chance of rain on Sunday. If the probability that it rains on both Saturday and Sunday is 10%, what is the probability that it rains over the weekend?

Solution

Let A be the event that it rains on Saturday and B be the event that it rains on Sunday.

P(A) = 0.25 and P(B) = 0.10

P(AB) = 0.10

Probability that it rains over the weekend

= P(AUB)

= P(A)+P(B)-P(AB)

= 0.25+0.25-0.10

= 0.40