Question

probability of raining on a day is 0.2
What is the probability of raining on exactly 2 days in a week ?

Answer 1

to chose 2 days in 7 days, use the 7C2 = 7!/(7-2)2! = 7!/5!2! = 21 ways
so, the probability of raining on exactly 2 days in a week is
21 * 0.2 * 0.2 = ...

Answer 2

Sorry but it is a wrong answer @RadEn