CSATTopicsQuantitative AptitudeMixture and Alligation

QUANTITATIVE APTITUDE

Mixture and Alligation — UPSC CSAT Previous Year Questions

Practice UPSC CSAT previous year questions from 2011–2026 classified underMixture and Alligation. Review the original question, four options, correct answer and explanation for every PYQ.

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5Total PYQs

2011–2026Years

2Subtopics

TOPIC-WISE PYQs

Mixture and Alligation

5 questions • 2011–2026

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Question 1

UPSC CSAT 2026Replacement

There are two chemicals which do not react with each other. A container contains 10 litres of the chemical A. One litre of this chemical is removed from it and one litre of the chemical B is poured. Then one litre of the mixture is removed from the container and one litre of B is poured. If this process of replacing one litre of the mixture by one litre of B is performed once more, then what is the volume of B that is present in the container approximately (in percentage)?

A25

B27

C29

D31

View Answer & Explanation+

Correct AnswerB

Explanation

After three replacement operations, the fraction of A is (9/10)^3=0.729, so B is 1−0.729=0.271, or about 27%. Hence B.

Question 2

UPSC CSAT 2022Replacement

There are two containers X and Y. X contains 100 ml of milk and Y contains 100 ml of water. 20 ml of milk from X is transferred to Y. After mixing well, 20 ml of the mixture in Y is transferred back to X. If m denotes the proportion of milk in X and n denotes the proportion of water in Y, then which one of the following is correct?

Am = n

Bm > n

Cm < n

DCannot be determined due to insufficient data

View Answer & Explanation+

Correct AnswerA

Explanation

After the first transfer, Y contains 20 ml milk and 100 ml water. The 20 ml returned to X contains 20/120 of milk, so X ends with 16 2/3 ml milk in 100 ml total; Y ends with the same proportion of water, 83 1/3/100. Hence the proportions are equal.

Question 3

UPSC CSAT 2020Replacement

A bottle contains 20 litres of liquid A. 4 litres of liquid A is taken out of it and replaced by the same quantity of liquid B. Again 4 litres of the mixture is taken out and replaced by the same quantity of liquid B. What is the ratio of quantity of liquid A to that of liquid B in the final mixture?

A4 : 1

B5 : 1

C16 : 9

D17 : 8

View Answer & Explanation+

Correct AnswerC

Explanation

After two replacements, A=20(16/20)^2=12.8 L and B=7.2 L, so the ratio is 16:9.

Question 4

UPSC CSAT 2016Alligation / Concentration

PASSAGE

30g of sugar was mixed in 180 ml water in a vessel A, 40 g of sugar was mixed in 280 ml of water in vessel B and 20 g of sugar was mixed in 100 ml of water in vessel C.

The solution in vessel B is:

Asweeter than that in C

Bsweeter than that in A

Cas sweet as that in C

Dless sweet than that in C

View Answer & Explanation+

Correct AnswerD

Explanation

Sugar concentration is 30/180 in A, 40/280 in B and 20/100 in C. B has the lowest concentration, so it is less sweet than C.

Question 5

UPSC CSAT 2015Alligation / Concentration

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

View Answer & Explanation+

Correct AnswerA

Explanation

Milk = 1/3+1/4=7/12 of one glass volume; water = 2/3+3/4=17/12. Ratio = 7:17.

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