Two trains run in the same direction at 40 km/h and 22 km/h and completely pass one another in 1 minute. If the first train is 125 m long, what is the length of the second train?

Introduction / Context:
For trains in the same direction, the relative speed is the difference of their speeds. The distance covered relative to each other to completely pass equals the sum of their lengths. Knowing total time and one length yields the other length.

Given Data / Assumptions:

• Speeds: 40 km/h and 22 km/h (same direction).
• Total pass time = 60 s.
• First train length L1 = 125 m; second length L2 = ?

Concept / Approach:
Relative speed v_rel = (40 − 22) km/h = 18 km/h = 5 m/s. Total relative distance = (L1 + L2) = v_rel * time.

Step-by-Step Solution:
L1 + L2 = 5 * 60 = 300 m.L2 = 300 − 125 = 175 m.

Verification / Alternative check:
At 5 m/s relative speed, 300 m needs 60 s, matching the given time.

Why Other Options Are Wrong:
125 m is the given first length; 150 or 200 m would make the combined pass distance inconsistent with 60 s at 5 m/s.

Common Pitfalls:
Adding speeds (for opposite directions) instead of subtracting for same direction.

Final Answer:
175 metres