two trains 180 m and 360 m long run at the speed of 60 kmph and 30 kmph in opposite directions in parallel tracks . the time which they take to cross each other is ?
"relative speed = 60 + 30 = 90 kmph * 5 / 18 = 25 m / s distance covered in crossing each other = 180 + 360 = 540 m required time = 540 * 1 / 25 = 21.6 sec answer is a"
divide(add(180, 360), multiply(add(60, 30), const_0_2778))