Pure milk costs ₹72 per litre. A milkman adds water to 25 litres of pure milk and sells the mixture at ₹60 per litre. How many litres of water does he add ?

5 litres

The correct answer is Option (2) → 5 litres

Cost of pure milk = ₹72 per litre

Quantity of pure milk = 25 litre

Selling price of the mixture = ₹60 per liter

let total quantity of water be x litre.

Total quantity of water = $(25+x)L$

Average cost price of mixture is,

$\frac{\text{Total cost of milk}}{\text{Total quantity of mixture}}=60$

$=\frac{72×25}{25+x}=60$

$⇒1800=60(25+x)$

$⇒300=60x$

$⇒x=\frac{300}{60}=5L$