A jar full of whisky contains 40% alcohol. A part of this whisky is replaced…

2023

A jar full of whisky contains 40% alcohol. A part of this whisky is replaced by another containing 19% alcohol and now the percentage of alcohol was found to be 26%. The quantity of whisky replaced is:

  1. A.

    1/4

  2. B.

    2/3

  3. C.

    2/6

  4. D.

    4/5

Attempted by 1 students.

Show answer & explanation

Correct answer: B

alligation diagram showing 40%, 26%, 19%

Algebraic solution:

Let the total quantity be 1 unit and let x be the fraction replaced.

  1. Alcohol remaining from original after removal: 0.4(1 - x).

  2. Alcohol added with replacement: 0.19x.

  3. Set their sum equal to the final alcohol amount (0.26):

  4. 0.4(1 - x) + 0.19x = 0.26 => 0.4 - 0.21x = 0.26 => 0.21x = 0.14

  5. x = 0.14 / 0.21 = 2/3.

Alligation (quick) check:

  • Difference between original concentration and final: 40% - 26% = 14.

  • Difference between final and replacement concentration: 26% - 19% = 7.

  • Ratio of original to replacement parts = 7 : 14 = 1 : 2, so the replaced part is 2 out of (1+2) = 3 parts, i.e. 2/3.

Final answer: 2/3

Explore the full course: Infosys Preparation