Question

The weather forecast for the weekend is a 35% chance of rain on Saturday and a 65% chance of rain on Sunday. Your friend says that means there is a 100% chance of rain this weekend. What error did your friend make?

Answer 1

Because these probabilities are independent, the friend was supposed to multiply them, not add them. So the probability of rain this weekend is

.35 × .65, or .2275, meaning that the probability of rain this weekend is 22.75%