Correct Answer - Option 4 : 252
Given:
A train x running at 74 km/h crosses another train y running at 52 km/h in the opposite direction in 12 seconds. The length of y is two-thirds that of x.
Concept Used:
When two trains crossing each other, their relative speed will be the sum of their speed.
1 km/h = (5/18) m/s
Distance = Time × speed
Calculation:
Relative speed (74 + 52) = 126 km/h
⇒ 126 × (5/18)
⇒ 35 m/s
Time taken to cross each other 12 second
Total distance covered (12 × 35) = 420 m
The length of y is two-thirds that of x
Let, the length of the train x is a meter
Accordingly,
(a + (2a/3) = 420
⇒ a = 420 × (3/5)
⇒ a = 252
∴ The length of the train X is 252 m