A cow costs more than 4 goats but less than 5 goats. If a goat costs between ₹ 600 and ₹ 800, which of the following is a most valid conclusion ?
- (a) A cow costs more than ₹ 2,500.
- (b) A cow costs less than ₹ 3,600.
- (c) A cow costs between ₹ 2,600 and ₹ 3,800.
- (d) A cow costs between ₹ 2,400 and ₹ 4,000. ✓ UPSC's answer
Why the answer is (d)
• A goat costs between ₹ 600 and ₹ 800, and a cow costs more than 4 goats but less than 5 goats.
• Lowest possible cow price: just over 4 × 600 = ₹ 2,400. Highest: just under 5 × 800 = ₹ 4,000.
• So all we can say for certain is that a cow costs between ₹ 2,400 and ₹ 4,000 — option (d).
• Hence option (d).
Why the other options are wrong
- (a) A cow costs more than ₹ 2,500.
- If a goat costs ₹ 610, a cow could cost ₹ 2,450, which is below ₹ 2,500.
- (b) A cow costs less than ₹ 3,600.
- If a goat costs ₹ 790, a cow could cost ₹ 3,900, which is above ₹ 3,600.
- (c) A cow costs between ₹ 2,600 and ₹ 3,800.
- The cow's price can fall outside ₹ 2,600–₹ 3,800, for example ₹ 2,450 or ₹ 3,900.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2015, held on 23 August 2015. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.