The probability of getting rain on any given day in June in Capital City is 1/10. What is the probability that it rains on at most 2 days in June? Express your answer as a decimal to the nearest thousandth.

tertre Sep 17, 2016

#1**+1 **

There are 30 days in June and we want to choose any two of them....this is a binomial probability problem

"At most" means it either rains 0 days, 1 day or 2 days

0 days = (9/10)^30 = 0.042391158275216203514294433201

1 day = C(30,1) (1/10)(9/10)^29 = 0.14130386091738734504764811067

2 days = C(30,2) * (1/10)^2 * (9/10)^28 = 0.227656220366901833687877511635

The sum of these = 0.411351239559505382249820055506 ≈ 0.411

CPhill Sep 17, 2016