A vessel full of water weighs 40 kg. If it is one-third filled, its weight becomes 20 kg. What is the weight of the empty vessel?
- (a) 10 kg ✓ UPSC's answer
- (b) 15 kg
- (c) 20 kg
- (d) 25 kg
Why the answer is (a)
• Let the empty vessel weigh V kg and a full load of water W kg.
• Full: V + W = 40. One-third full: V + W/3 = 20.
• Subtracting, 2W/3 = 20, so W = 30 and V = 10.
• Hence option (a).
Why the other options are wrong
- (b) 15 kg
- 15 kg is incorrect because it does not satisfy the condition that one-third of the water weight plus the vessel weight equals 20 kg.
- (c) 20 kg
- 20 kg is incorrect because if the vessel weighed 20 kg, the full water weight would be 20 kg, making the one-third filled weight 26.67 kg, not 20 kg.
- (d) 25 kg
- 25 kg is incorrect because if the vessel weighed 25 kg, the full water weight would be 15 kg, making the one-third filled weight 30 kg, not 20 kg.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.