2020 CSAT, all questions
UPSC Prelims 2020 · CSAT
Question 79: Basic Numeracy
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?
a10 kg
b15 kg
c20 kg
d25 kg
AnswerUPSC’s answer is (a).
Let the empty vessel weigh e and the water in a full vessel weigh w. Then e + w = 40 and e + w/3 = 20. Subtracting gives 2w/3 = 20, so w = 30 and e = 10 kg. Check: one-third of 30 is 10, and 10 + 10 = 20.
Why each option is right or wrong
- (a) Right: the empty vessel weighs 10 kg.
- (b) With 15 kg empty, the water would be 25 kg and one-third of it would give 23.3 kg.
- (c) With 20 kg empty, the water would be 20 kg and one-third of it would give 26.7 kg.
- (d) With 25 kg empty, the water would be 15 kg and one-third of it would give 30 kg.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.