Question

A train passes a platform in 36 seconds. The same train passes a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, the length of the platform is

Answer 1

Length of train =

$= (54 \times \frac{5}{18} ) \times 20 \\ = 15 \times 20 \\ = 300 \: metres.$

Now,
lets length of platform be L
then,

$\frac{300 + l}{54 \times \frac{5}{18} } = 36 \\ \frac{300 + l}{15} = 36 \\ 300 + l = 36 \times 15 \\ 300 + l = 540 \\ l = 540 - 300 = 240 \: metres.$

Length of platform is 240 metres.