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UPSC 1995: A person travelled from one place to another at an average speed of 40 kilometres/hour and back to the original place at an average speed of 50 kilometres/hour. What is his average speed in kilometres/hour during the entire roundtrip?
(a)45
(b)20
(c)400/9
(d)Impossible to find out unless the distance between the two places is known
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Not attemptedCorrect Answer: (c) 400/9
For equal distances the average speed is the harmonic mean: 2·40·50 / (40+50) = 400⁄9 km h⁻¹ ≈ 44.44 km h⁻¹, which is option (c). The figure is not 45 or 20, and the distance is immaterial because it cancels in the harmonic-mean formula. ([id.scribd.com](https://id.scribd.com/document/731910046/1995))
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Frequently Asked Questions
What is the correct answer to this UPSC 1995 Science & Technology question?▼
The correct answer is option (c): 400/9. Watch the detailed video explanation in our Sherlocking Prelims course on UnlockIAS.
Which year was this Quantitative Aptitude question asked in UPSC Prelims?▼
This question was asked in UPSC CSE Prelims 1995, GS Paper 1, as Question 136. It falls under Science & Technology > Quantitative Aptitude.
What is the difficulty level of this UPSC question?▼
This question is rated "easy". It tests basic recall and most well-prepared aspirants should answer it correctly.
How many UPSC Prelims questions have been asked from Quantitative Aptitude?▼
UPSC has asked 178 questions from Quantitative Aptitude (under Science & Technology) across multiple years. Visit the topic page to see the full list and year-wise trends.