A jogger running at 9 kmph alongside a railway track in 240 metres ahead of the engine of a 120 metres long train running at 45 kmph in the same direction. In how much time will the train pass the jogger?

A. 36 sec
B. 40 sec
C. 30 sec
D. 20 sec

Solution:

\[\left. \begin{array} { l } { \text { Speed of train relative to jogger } }\\
{= ( 45 – 9 ) km / hr = 36 km / hr . } \\ { = ( 36 \times \frac { 5 } { 18 } ) m / sec } \\ { = 10 m / sec } \\ { \text { Distance to be covered } = ( 240 + 120 ) m }\\
{= 360 m . } \\ { \therefore \text { Time taken } = ( \frac { 360 } { 10 } ) sec = 36 sec . } \end{array} \right.\]

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