Multiple choice

A train covers a certain distance in two halves. It travels at 210 km/hr for the first half and at 240 km/hr for the second half. If the train takes 20 hours to finish the journey, find the total distance travelled.

  1. 4480 km

  2. 4000 km

  3. 3600 km

  4. 4500 km

  5. 5480 km
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A Correct answer
Explanation

Let total distance be D. Time for first half = (D/2) / 210 = D/420. Time for second half = (D/2) / 240 = D/480. Total time = D/420 + D/480 = 20. D(8+7)/3360 = 20 => 15D/3360 = 20 => D = (20*3360)/15 = 4480.

AI explanation

Let d be the total distance, so each half of the distance is d/2 kilometres. Using the time formula, time equals distance divided by speed, and the sum of the times for both halves equals 20 hours. The equation is (d/2)/210 + (d/2)/240 = 20, which simplifies to d/420 + d/480 = 20. Finding a common denominator gives (16d + 14d)/6720 = 20, meaning 30d = 134400, so the total distance d is 4480 km.

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