Question

Rajan sitting inside a train travelling at a speed of 108 km/h crosses another train running in the same direction in 47 seconds. Find the sum of the length of both trains, if the speed of the slower train is 25 m/s and the length of the faster train is two times the length of the slower train.
1. 600 m
2. 650 m
3. 690 m
4. 705 m 

Answer 1

Correct Answer - Option 4 : 705 m 

Given :

Rajan sitting inside a train travelling at a speed of 108 km/h crosses another train running in the same direction in 47 seconds.

The speed of the slower train is 25 m/s and the length of the faster train is two times the length of the slower train.

Formula used :

Time = Distance/Speed 

Calculations :

Let the length of the slower train be 'L' m 

Speed of the faster train in m/s = 108 × (5/18) = 30 m/s 

Speed of slower train = 25 m/s 

According to the question 

47 = (length of the slower train)/Relative speed 

⇒ 47 = L/(30 - 25)       (when train move in same direction relative speed is the difference of the speeds)

⇒ l = 47 × 5 = 235 m 

Now length of faster train = 2 × L = 2L 

⇒ 470 m 

Total length of both the trains = 235 + 470 = 705 m 

∴ The length of both the trains will be 705 m