Correct Answer - Option 2 : 9 minutes
Given:
A train crosses a platform in 3 minutes
Length of train = Length of platform
Length of bridge = 5 × Length of train
Concept:
Speed of train is constant during the journey
Formula used:
Speed = Distance/Time
Calculation:
Let the length of the train be L
Let the train crosses the bridge in 't' minutes
Speed of train = (The length of train + The length of the platform)/(Time of crossing)
⇒ 2L/3
Speed of train = (The length of train + The length of bridge)/(Time of crossing)
⇒ 6L/t
Using concept, we get
⇒ 2L/3 = 6L/t
⇒ t = 3 × 3
⇒ t = 9 minutes
∴ The train crosses the bridge in 9 minutes.
