The fuel cost per hour for a train is v²/4 rupees, where v is the speed in km/h. Other costs are ₹100 per hour. Find the most economical speed for a journey.
The fuel cost per hour for a train is v²/4 rupees, where v is the speed in km/h. Other costs are ₹100 per hour. Find the most economical speed for a journey.
- A. 10 km/h
- B. 15 km/h
- C. 20 km/h
- D. 25 km/h
Answer: C) 20 km/h
Explanation: Time t = D/v. Total Cost C = (v²/4 + 100)(D/v) = D(v/4 + 100/v). dC/dv = D(1/4 - 100/v²) = 0 → v² = 400 → v = 20 km/h.
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