A milkman buys milk at ₹40 a litre, adds water, and sells the mixture at ₹40 a litre, making a 25% profit. In what ratio are water and milk in the mixture?

1 : 4Correct answerYour answer1 : 5Correct answerYour answer1 : 3Correct answerYour answer4 : 1Correct answerYour answer

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CorrectNot quiteAnswer A

Correct answer: A

A 25% profit means the cost of a litre of the mixture is $\frac{40}{1.25} = 32$ rupees.
Water : milk $= (40 - 32) : (32 - 0) = 8 : 32 = 1 : 4$ .

Worth noting

$1 : 5$ treats 25% profit as water being a fifth of the mixture; profit is reckoned on the cost, so water is a quarter of the milk.

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