Question

Two trains are running in opposite directions on parallel tracks at the speeds of 42 km/h and 57 km/h, respectively. They take 18 seconds to cross each other. If the length of one train is 295 m, then the length (in m) of the other train is:
1. 245
2. 200
3. 300
4. 225

Answer 1

Correct Answer - Option 2 : 200

Given:

Speed of first train = 42 km/hr

Speed of second train = 57 km/hr

Total time taken to cross each other = 18 seconds

Length of on train = 295m

Concept used:

Two trains are running in opposite directions on parallel tracks then the relative speed is sum of the speeds

Formula used:

Relative speed = Speed of first train + speed of second train 

Distance = speed × time

a km/hr = 5/18 m/sec

Calculations:

Relative speed = 42 + 57

⇒ 99 km/hr

99 km/hr = 99 × 5/18

⇒ 55/2 m/sec

Distance covered = 295 + x

⇒ 295 + x = 55/2 × 18

⇒ 295 + x = 55 × 9

⇒ x = 495 - 295 

⇒ x = 200

∴ The length of second train is 200 m