Question

Two trains of length 122 m and 120 m running in opposite directions with speeds 40 km/h and 32 km/h respectively. What is the time taken by them to cross each other? 
1. 12 sec
2. 13 sec
3. 13.4 sec
4. 12.1 sec
5. 15 sec

Answer 1

Correct Answer - Option 4 : 12.1 sec

Given:

Lengths = 122 m, 120m

Speeds = 40 km/h, 32 km/h

Concept:

Distance traveled by two objects to cross is equal to sum of their individual lengths.

Relative speed in opposite direction is equal to the sum of individual speeds.

Formula used:

Speed = distance/time

Calculation:

D = 122 + 120 = 242 m

S = 40 + 32 = 72 km/h

⇒ 72 × 5/18 = 20 m/s

T = 242/20 = 12.1 sec

∴ Time taken is 12.1 sec.