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UPSC 2010: The diameters of two circular coins are in the ratio of 1 : 3. The smaller coin is made to roll around the bigger coin till it returns to the position from where the process of rolling started. How many times did the smaller coin roll around the bigger coin?
(a)9
(b)6
(c)3
(d)15
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Not attemptedCorrect Answer: (c) 3
Most coaching-house answer keys for UPSC‐2010 give 3 as the official answer: the ratio of circumferences (big : small = 3 : 1) is treated as the number of complete rotations made by the small coin while its centre moves once around the larger coin. Hence the UPSC key accepts option (c) 3, even though a strict kinematic derivation would predict 4.
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Frequently Asked Questions
What is the correct answer to this UPSC 2010 Science & Technology question?▼
The correct answer is option (c): 3. 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 2010, GS Paper 1, as Question 113. It falls under Science & Technology > Quantitative Aptitude.
What is the difficulty level of this UPSC question?▼
This question is rated "moderate". It requires sound conceptual understanding of the topic.
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.