A train’s onward speed is 25% more than its return speed. It halts 1 hour at the destination. Total time for a round trip of 800 km is 17 h (including the 1 h halt). What is the onward (faster) speed (in km/h)?

Introduction / Context:Let return speed be v; onward speed is 1.25v. One-way distance is 400 km. Exclude the 1 h halt first to get actual travel time, then solve for v from the total-time equation.

Given Data / Assumptions:

• Total distance = 800 km.
• Halt = 1 h; total time = 17 h ⇒ travel time = 16 h.
• Onward speed = 1.25v; return speed = v.

Concept / Approach:Travel time T = 400/(1.25v) + 400/v = 16. Solve for v, then compute 1.25v.

Step-by-Step Solution:

Verification / Alternative check:Times: 400/56.25 = 7.111... h; 400/45 = 8.888... h; sum ≈ 16 h; +1 h halt = 17 h total.

Why Other Options Are Wrong:45 km/h is the return speed, not onward; others misfit the 16 h travel time.

Common Pitfalls:Forgetting to subtract the 1 h halt before solving for speeds.

Final Answer:56.25 km/h