A 40-litre mixture of milk and water is 25% water. How much milk must be added so that water is 20% of the mixture?

2 litresCorrect answerYour answer8 litresCorrect answerYour answer10 litresCorrect answerYour answer11 litresCorrect answerYour answer

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CorrectNot quiteAnswer C

Correct answer: C

Water: $0.25 \times 40 = 10$ litres, and adding milk does not change it.
10 litres must be 20% of the new total: total $= 50$ litres, so add $50 - 40 = 10$ litres of milk.

Worth noting

2 litres treats 25% − 20% = 5% of 40 litres as the milk needed.

Ten questions from Alligation & Mixtures, at your own pace.

Ten questions from Alligation & Mixtures, at your own pace.

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