Trains — clearing time when two trains approach each other: Two trains 512 m and 528 m long run towards each other at 84 km/h and 60 km/h. From the moment they meet, in how many seconds will they clear each other completely?

Introduction / Context:
This is a standard relative-speed problem for trains moving in opposite directions. The time to completely cross equals (sum of lengths) / (relative speed).

Given Data / Assumptions:

• Lengths: 512 m and 528 m.
• Speeds: 84 km/h and 60 km/h in opposite directions.

Concept / Approach:
Convert speeds to m/s, add them to get relative speed, add train lengths, then compute time = distance / speed.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• 25 s, 15 s, 27 s are inconsistent with the computed 26 s.

Common Pitfalls:

• Forgetting to convert km/h to m/s correctly (multiply by 5/18).
• Using difference of speeds instead of sum for opposite directions.

Final Answer:
26 s