UPSC Prelims 2012 · CSAT
Question 62: Basic Numeracy
Two glasses of equal volume are respectively half and three-fourths filled with milk. They are then filled to the brim by adding water. Their contents are then poured into another vessel. What will be the ratio of milk to water in this vessel ?
AnswerUPSC’s answer is (d).
Take the volume of each glass as 1 unit. The first glass holds 1/2 milk and, after topping up, 1/2 water; the second holds 3/4 milk and 1/4 water. Together, milk is 1/2 + 3/4 = 5/4 and water is 1/2 + 1/4 = 3/4. So the ratio of milk to water in the vessel is 5/4 : 3/4, which is 5 : 3. Remember: add the milk and the water separately across the two glasses.
Why each option is right or wrong
- (a) Wrong. 1 : 3 would mean far too little milk.
- (b) Wrong. The totals are 5/4 milk to 3/4 water, so there is more milk than water.
- (c) Wrong. The totals are 5/4 milk to 3/4 water, which is not 3 : 2.
- (d) Right. Milk 5/4 to water 3/4 is 5 : 3.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.