Question

A train travelling at 42km/hr passes a cyclist going in the same direction in 9 secs.; if the cyclist had been going in the opposite direction, the train would have passed him in 5 secs. Find the length of the train

Answer 1

Answer:

Let the length of the train be x meter

and the speed of the cyclist is y m/s

Now when the train and the cyclist are in the same direction, the relative speed is :(35/3-y)m/s[converting 42km/h to m/s-35/3m/s]

Now distance/relative speed =9 seconds

Substituting the values, we get x+9y.....................(1)

Similarly calculate the relative speed when they are in the opposite direction

The relative speed is (35/3+y)

Now distance/relative speed is equivalent to 5 seconds

Substituting the values, we get the equation

3x-15y=175.................................(2)

Solving (1) and (2), we get x=75 meters

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