two trains 50 m and 120 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks . the time which they take to cross each other is ?
"relative speed = 60 + 40 = 100 km / hr . = 100 * 5 / 18 = 250 / 9 m / sec . distance covered in crossing each other = 50 + 120 = 170 m . required time = 170 * 9 / 250 = 6.12 = 6.12 sec . answer : c"
divide(add(50, 120), multiply(add(60, 40), const_0_2778))