Problem: if the population of a certain country increases at the rate of one person every 15 seconds , by how many persons does the population increase in 10 minutes ?
Rationale: "since the population increases at the rate of 1 person every 15 seconds , it increases by 4 people every 60 seconds , that is , by 4 people every minute . thus , in 10 minutes the population increases by 10 x 4 = 40 people . answer . a ."
annotated_formula: multiply(divide(const_60, 15), 10)