Question

What was the speed of the superfast train in m/s, if it crossed the Mumbai railway station platform which was 0.7 km long in 40 seconds? The length of the superfast train is half of the length of the Mumbai railway station platform. 

1. 30 m/sec 
2. 26.25 m/sec
3. 35 m/sec
4. 40 m/sec

Answer 1

Correct Answer - Option 2 : 26.25 m/sec

Given : 

The length of platform = 0.7 km 

Time to cross the platform by superfast train = 40 sec 

Formula: 

Distance = speed × time 

Calculation: 

1 km = 1000 m 

⇒ Length of platform = 0.7 x 1000 = 700 m 

⇒ Length of train = ½ × 700 = 350 m 

⇒ Distance = speed × time 

⇒ length of train + length of platform = speed of train × 40 sec

⇒ 1050 = speed of train × 40 sec

⇒ speed of train = 1050/40 = 26.25 m/s 

∴ Speed of superfast train = 26.25 m/s