Problem: if the probability of rain on any given day in chicago during the summer is 20 % , independent of what happens on any other day , what is the probability of having exactly 3 rainy days from july 4 through july 7 inclusive ?
Rationale: "one possible case is : rainy - rainy - rainy - not rainy . the probability of this case is 1 / 5 * 1 / 5 * 1 / 5 * 4 / 5 = 4 / 625 the number of possible cases is 4 c 3 = 4 . p ( exactly 3 rainy days ) = 4 * 4 / 625 = 16 / 625 the answer is e ."
annotated_formula: multiply(4, power(divide(const_1, const_2), 4))