Problem: a train covers a distance of 10 km in 20 min . if it takes 6 sec to pass a telegraph post , then the length of the train is ?
Rationale: "speed = ( 10 / 20 * 60 ) km / hr = ( 30 * 5 / 18 ) m / sec = 8.333333 m / sec . length of the train = 8.333333 * 6 = 50 m . answer : a"
annotated_formula: divide(10, subtract(divide(10, 20), 6))