If the probability of rain on any given day in City X is 40%, what is probability that it rains on exactly 3 days in a 4 day period?
Choices.
A) 16/25  B) 48/125  C) 96/625  D) 108/625  E) 132/625
One possible way is rain-rain-rain-no rain.   The probability of this is 2/5*2/5*2/5*3/5 = 24/625   The number of possible ways is 4C3 = 4, so we multiply this by 4.   P(rain on exactly 3 days) = 4*24/625 = 96/625   The answer is 96/625.
<result>C</result>
If the probability of rain on any given day in City X is 40%, what is probability that it rains on exactly 3 days in a 4 day period?