UPSC Prelims 2015 CSAT Paper II · Q35 of 74 Basic Numeracy easy

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 ?

  1. (a) 7 : 17 ✓ UPSC's answer
  2. (b) 1 : 3
  3. (c) 9 : 21
  4. (d) 11 : 23

Why the answer is (a)

• Let the capacity of each glass be 12 units (LCM of 3 and 4) to simplify calculations.

• The first glass contains 1/3 of 12 = 4 units of milk and is filled with 8 units of water.

• The second glass contains 1/4 of 12 = 3 units of milk and is filled with 9 units of water.

• Total milk in the pot is 4 + 3 = 7 units.

• Total water in the pot is 8 + 9 = 17 units.

• Therefore, the ratio of milk to water is 7 : 17.

Why the other options are wrong

(b) 1 : 3
Option (b) 1:3 is incorrect because the total milk is 7 units and total water is 17 units, not 1 and 3.
(c) 9 : 21
Option (c) 9:21 is incorrect because the calculated milk quantity is 7 units, not 9 units.
(d) 11 : 23
Option (d) 11:23 is incorrect because the sum of milk and water is 24 units, not 34 units, and the milk portion is 7, not 11.

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.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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