Question

Wanda is working on her predictions for the next few days. She calculates that there is a 20% chance of rain on Monday and a 20% chance of rain on Tuesday. If she is correct, what is the probability that it will rain on at least one of these days?

Answer 1

36%

Explanation:

the complement of it raining on at least one of these days = it not raining on any day

this means that if it does not rain on at least one day, it does not rain on any day

thus,

1 - probability of it not raining at all = probability it rains at least one day

probability it doesn't rain on monday = 1- 20% = 80%

probability it doesn't rain on tuesday = 1 - 20% = 80%

probability it doesn't rain on monday AND it doesn't rain on tuesday = probability it doesn't rain at all

P(A and B) = P(A) * P(B) = 0.8 * 0.8 = 0.64

1 - 0.64 = 0.36 as our answer