A train traveling at 36 km/hr completely passes another train at 50% more speed but 50% of its length in the opposite direction in 12 secs. It takes 90 secs for the same train to pass a platform. Find the length of the platform.
- 700 meters
- 900 meters
- 950 meters
- 1000 meters
- 1100 meters
The Usual Method
Speed of slower train = 36 km/hr = 10 mt/sec
Speed of faster train = 36 x 1.5 = 54 km/hr = 15 mt/sec
Let the length of the slower train be 2l.
length of the faster train =
Using the concept of relative speed, we get:
Let the length of the platform be ‘x’ meters.
Using relative speed concepts, we get:
Estimated Time to arrive at the answer = 45 seconds.
Note that it takes 90 secs for the train traveling at the speed of 10 mt/sec (36 km/hr) to traverse a length equal to its own plus that of the platform.
i.e. length of train + length of platform = 90
length of train + length of platform = 90 x 10 = 900 meters.
Hence, the length of platform has to be < 900 meters. Hence 700 meters (option ‘1’).
Estimated Time to arrive at the answer = 10 seconds.