In 12 seconds, a train travelling at 48 kilometres per hour crosses another train travelling in the opposite direction at 42 kilometres per hour. It also takes 45 seconds to pass a railway platform. The platform's length is 12 feet.
A. 400 m
B. 450 m
C. 560 m
D. 600 m
Answer:A
In 12 seconds, a train travelling at 48 kilometres per hour crosses another train travelling in the opposite direction at 42 kilometres per hour. It also takes 45 seconds to pass a railway platform. The platform's length is 12 feet.
A. 400 m B. 450 m C. 560 m D. 600 m
Explanation: Let the first train's length be x metres.The length of the second train is then ( x/2 ) metres. (48 + 42) kmph = (90 x 5/18) m/sec = 25 m/sec Relative speed = (48 + 42) kmph.As a result, [x + (x/2)]/25 = 12 or 3x/2 = 300 or x = 200.As a result, the initial train's length is 200 metres.Let the platform's length be y metres.The first train's speed is ( 48 x 5/18 ) m/sec, or 40/3 m/sec. As a result, (200 + y) x 3/40 = 45.=> 1800 = 600 + 3y=> 400 m for y.