Problem: the present population of a town is 3888 . population increase rate is 20 % p . a . find the population of town before 2 years ?
Rationale: "p = 3888 r = 20 % required population of town = p / ( 1 + r / 100 ) ^ t = 3888 / ( 1 + 20 / 100 ) ^ 2 = 3888 / ( 6 / 5 ) ^ 2 = 2700 ( approximately ) answer is e"
annotated_formula: add(3888, divide(multiply(3888, 20), const_100))