A train 180 m long moving at the speed of 20 m/sec passes across a boy who is moving at a speed of 10 m/sec in the direction of the train. The time (in s) taken by the train to over take the boy is:

18

Relative speed = 20 - 10 = 10 m/sec

( when moves in same direction )

Length of train = 180  m

Time required by train to overtake the boy ,

=  \(\frac{180}{10}\) m/sec 

= 18 sec