Problem: a train covers a distance of 12 km in 10 min . if it takes 6 sec to pass a telegraph post , then the length of the train is ?
Rationale: "speed = ( 12 / 10 * 60 ) km / hr = ( 72 * 5 / 18 ) m / sec = 20 m / sec . length of the train = 20 * 6 = 120 m . answer : c"
annotated_formula: divide(const_100.0, subtract(divide(const_100.0, 10), 6))