# How much water should be added to 40 litres of milk at Rs. 25 a litre so as to have a mixture worth Rs. 20 a litre?

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How much water should be added to 40 litres of milk at Rs. 25 a litre so as to have a mixture worth Rs. 20 a litre?
1. 15 litre
2. 16 litre
3. 12 litre
4. 11 litre
5. 10 litre

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Correct Answer - Option 5 : 10 litre

Given

40 liter milk price at Rs = 25 per kg

Calculation

Let the quantity of water to be added be x litres.

Cost of 40 litres of milk at Rs. 25 a litre = 40 × 25 = Rs. 1000

∴ Quantity of the mixture = 40 + x litres

∴ Cost of mixture at Rs. 20 a litre = (40 +x)20 = Rs. (800 + 20x)

∴ 800 + 20x = 1000

or, 20x = 200

∴ x = 10 litres

Water added in pure milk is = 10 liters