Correct Answer - Option 3 : 9 : 4
Given:
Length of train = 180 m
Speed of the train = 54 km/hr
Train crosses a platform in 20 seconds and crosses a tunnel in 30 seconds.
Formula Used:
Distance = Speed × Time
Calculation:
Suppose the length of the platform and the tunnel is x m and y m, respectively.
Speed of the train = 54 × 5/18 = 15 m/s
Case I: Train crosses the platform in 20 seconds
⇒ (180 + x) = 15 × 20
⇒ 180 + x = 300
⇒ x = 120 m
The length of the platform is 120 m.
Case II: Train crosses the tunnel in 30 seconds.
⇒ (180 + y) = 15 × 30
⇒ 180 + y = 450
⇒ y = 450 – 180
⇒ y = 270 m
the ratio between the length of tunnel and the length of the platform is 270 : 120 = 9 : 4
∴ Required ratio is 9 : 4