A bullet train covers a fixed distance in 30 minutes at an average speed of 240 km/h. Due to track maintenance, it needs to be di…

Question

A bullet train covers a fixed distance in 30 minutes at an average speed of 240 km/h. Due to track maintenance, it needs to be diverted, increasing the distance by 20%. If the train needs to arrive at its destination on time (i.e., in 30 minutes), what should its new average speed be in km/h?

1. A. 280 km/h
2. B. 300 km/h
3. C. 288 km/h (Correct answer)
4. D. 320 km/h

Correct Answer

Option C — 288 km/h

Detailed Solution & Explanation

The correct answer is 288 km/h.

Key Points

• Original distance = 240 × 0.5 h = 120 km.
• The diversion adds 20%: new distance = 120 × 1.2 = 144 km, still to be covered in 30 min = 0.5 h. Required speed = 144 / 0.5 = 288 km/h.
• The time is fixed, so the speed must scale with the distance — a 20% longer route needs a 20%-faster speed (240 × 1.2 = 288), confirming the answer.