Question

Hello Brothers and sisters please help -

Two trains, 100 m and 80 m long, are running on parallel tracks. While running in opposite directions, they cross each other in 9 seconds .While running in the same direction ,the faster train passes the other one in 18 seconds .Find the speed of the two trains in km/hr.

Answer 1

hey mate.
here's the solution

Answer 2

Let the speed of the Faster train be x and Slower train be y.

Total distance to be traveled = 100 + 80 = 180.

We know that Time = Distance/Speed.

(i)

While running in opposite directions, they cross each other in 9 seconds.

⇒ x + y = 180/9

⇒ x + y = 20

(ii)

While running in same direction, the faster train passes other one in 18 sec.

⇒ x - y = 180/18

⇒ x - y = 10

On solving (i) & (ii), we get

⇒ x + y = 20

⇒ x - y = 10

   --------------

     2x = 30

       x = 15.

Substitute x = 15 in (ii), we get

⇒ x - y = 10

⇒ 15 - y = 10

⇒ y = 5.

Hence,

⇒ Speed of faster train = 15 m/sec {1 m/sec = 3.6 km/hr}

                                       = 15 * 3.6

                                       = 54 km/hr.

⇒ Speed of Slower train = 5 m/sec

                                         = 5 * 3.6

                                        = 18 km/hr.

Therefore:

⇒ Speed of Faster train = 54 km/hr.

⇒ Speed of Slower train = 18 km/hr.

Hope this helps!