two goods trains each 500 m long are running in opposite directions on parallel tracks . their speeds are 50 km / hr and 30 km / hr respectively . find the time taken by the slower train to pass the driver of the faster one ?
"relative speed = 50 + 30 = 80 km / hr . 80 * 5 / 18 = 200 / 9 m / sec . distance covered = 500 + 500 = 1000 m . required time = 1000 * 9 / 200 = 45 sec . answer : c"
add(50, 30)