Multiple choice general knowledge math & puzzles

if i travel half my distance at 40kmph and the other half at 60 kmph whats my average speed for the whole journey

  1. 50kmph

  2. 45kmph

  3. 53kmph

  4. 48kmph
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For equal distances, average speed is the harmonic mean, not arithmetic mean. Total distance = 2d. Time for first half = d/40, time for second half = d/60. Total time = d/40 + d/60 = 5d/120. Average speed = 2d / (5d/120) = 240/5 = 48 kmph. The arithmetic mean (50 kmph) is incorrect.

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