Problem: a train 250 m long passes a man , running at 10 km / hr in the same direction in which the train is going , in 20 seconds . the speed of the train is :
Rationale: "speed of the train relative to man = 250 / 20 m / sec = 25 / 2 m / sec . = 25 / 2 x 18 / 5 km / hr = 45 km / hr . let the speed of the train be x km / hr . then , relative speed = ( x - 10 ) km / hr . x - 10 = 45 = 55 km / hr . answer : c"
annotated_formula: divide(divide(subtract(250, multiply(multiply(10, const_0_2778), 10)), 10), const_0_2778)