2015 CSAT, all questions
UPSC Prelims 2015 · CSAT
Question 35: Basic Numeracy
Two equal glasses of same type are respectively 1/3 and 1/4 full of milk. They are then filled up with water and the contents are mixed in a pot. What is the ratio of milk and water in the pot ?
a7 : 17
b1 : 3
c9 : 21
d11 : 23
AnswerUPSC’s answer is (a).
Take the glass capacity as 12 units to avoid fractions. Milk in the first glass = 12 ÷ 3 = 4; in the second = 12 ÷ 4 = 3. Total milk = 7. Total mixture = 24, so water = 24 − 7 = 17. The ratio of milk to water is 7 : 17.
Why each option is right or wrong
- (a) Right: milk 7 and water 17 out of 24.
- (b) Wrong: 1 : 3 would be 6 milk to 18 water.
- (c) Wrong: 9 : 21 = 3 : 7 would give 7.2 units of milk out of 24, not 7.
- (d) Wrong: 11 : 23 would give about 7.8 units of milk out of 24, not 7.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2015, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.