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Distance = 20 km Speed of A = 4 km per hour Speed of B = 2 km per hour Speed of C = 10 km per hour Time = Distance/speed Time taken by A = 20/4 hours = 5 hours Time taken by B = 20/2 hours = 10 hours Time taken by C = 20/10 hours = 2 hours The required time = LCM of 5, 10, 2 = 10 ∴ All three will meet again at starting point after 10 hours
A train 400 metre long takes 40 sec to cross a man running at a speed of 4 km/hr in the direction same to that of train. What is the speed of the train?
A train running at 90 km/h crosses an electric pole in 18 seconds and a platform in 55 seconds. What is the length of the platform?