# Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is:

A. 60 m
B. 40 m
C. 50 m
D. 30 m

Solution:

$\left. \begin{array} { l } { \text { Let the length of each train be } x \text { metres. } } \\ { \text { Then, distance covered } = 2 x \text { metres. } } \\ { \text { Relative speed } = ( 46 – 36 ) km / hr } \\ { = ( 10 \times \frac { 5 } { 18 } ) m / sec } \\ { = ( \frac { 25 } { 9 } ) m / sec } \\ { \therefore \frac { 2 x } { 36 } = \frac { 25 } { 9 } } \\ { \Rightarrow 2 x = 100 } \\ { \Rightarrow x = 50 } \end{array} \right.$