Problem: if the probability of rain on any given day in chicago during the summer is 50 % , independent of what happens on any other day , what is the probability of having exactly 3 rainy days from july 4 through july 9 inclusive ?
Rationale: "one possible case is : rainy - rainy - rainy - not rainy - not rainy - not rainy . the probability of this case is ( 1 / 2 ) ^ 6 = 1 / 64 the number of possible cases is 6 c 3 = 20 . p ( exactly 3 rainy days ) = 20 * 1 / 64 = 5 / 16 the answer is b ."
annotated_formula: multiply(4, power(divide(const_1, const_2), 4))