For a certain weekend, the weatherman predicts that it will rain with a 40% probability on Saturday and a 50% probability on Sunday. Assuming these probabilities are independent, what is the probability that it rains over the weekend (that is, on at least one of the days) ? Express your answer as a percentage.

70%

Step-by-step explanation:

The probability it rains on at least one of the days is:

P = P (Sat & not Sun) + P (Sun & not Sat) + P (Sat & Sun)

P = (0.40) (1-0.50) + (0.50) (1-0.40) + (0.40) (0.50)

P = 0.20 + 0.30 + 0.20

P = 0.70

Another way to look at it is 1 - the probability that it doesn't rain on either day.

P = 1 - P (not Sat & not Sun)

P = 1 - (1-0.40) (1-0.50)

P = 1 - 0.30

P = 0.70

There is a 70% probability that it will rain on at least one day.