Pure milk costs Rs. 75 per litre. A milkman adds water to 28 liters of pure milk and sells the mixture at Rs. 60 per litre. How many liters of water does he add?

7

The correct answer is Option (3) → 7

$\text{Let water added be }x\ \text{litres}$

$\text{Cost price of mixture per litre}=\frac{75\times 28}{28+x}$

$\frac{75\times 28}{28+x}=60$

$2100=60(28+x)$

$2100=1680+60x$

$60x=420$

$x=7$

$\text{Water added} = 7\ \text{litres}$