Question

A train of length 250 m can cross a platform in 20 seconds with a speed of 90 km/h. Find in how much time the train will cross the bridge that is 40% longer the length of the platform.
1. 24 seconds
2. 28 seconds
3. 32 seconds 
4. 18 seconds 

Answer 1

Correct Answer - Option 1 : 24 seconds

Given :

A train of length 250 m can cross a platform in 20 seconds with a speed of 90 km/h

The length of the bridge is 40% more than the length of the platform. 

Formula used :

Time = Distance/Speed 

Calculations :

Let the length of the platform be 'P' m

Speed of the train is '90' km/h or 25 m/s    (18 km/h = 5 m/s) 

According to the question 

20 = (250 + P)/25 

⇒ P = 250 m 

Now time taken to cross the bridge will be 

Length of bridge = 250 + 40% of 250        (bridge is 40% more than the length of platform)

⇒ 350 m

Time to cross the bridge = (Length of train + length of bridge)/Speed of train 

⇒ (250 + 350)/25    

⇒ 24 seconds 

∴ Option 1 will be the correct choice.