A train travelling at 36 kmph takes 48 seconds to cross a bridge. It then crosses a man cycling at the rate of 9 kmph in the same direction in 20 seconds. Find the length of the bridge.
Answer & explanation
Correct answer: option 4
Speed = \(\frac{ Distance}{ Time}\)
Let the length of the train be x and the length of bridge be y
So, according to the question:
(36 - 9) x \(\frac{5 }{18 }\) = \(\frac{ x}{ 20}\)
27 x \(\frac{5 }{18 }\) = \(\frac{ x}{ 20}\)
x = 150
Length of the train is 150 m
According to the question,
36 x \(\frac{5 }{18 }\) = \(\frac{ \text{150 + y}}{ 48}\)
10 = \(\frac{ \text{150 + y}}{ 48}\)
480 = 150 + y
y = 330
Thus, the length of the bridge is 330 m