Question

Two trains of same length take 6 sec and 9 sec, respectively to cross a pole. if both the trains are running in the same direction, then how long will they take to cross each other?

Answer 1

Let the length of the train be x m each .

speed with time 6 s = x / 6 m/s

speed with time 9 s = x / 9 m/s

As running in the same direction

net speed= x / 6 - x / 9 = (3x - 2x)/18 = x/18 m/s

Distance covered to cross each other = 2x

so, time = 2x / (x/18) = 2x × 18/x = 36 s

So, it will take 36 seconds to cross each other.

Answer 2

Answer:

36s

Explanation:

Lets assume distance=54m (lcm of 6 and 9)

Distance/speed=time

54+54/9-6=108/3=36s

(Note: As there are two trains of same length, so 54+54=108.

speed=distance/time, 54/6=9 and 54/9=6)