Five litres of water is added to a certain quantity of pure milk costing ₹60 per litre. If by selling the mixture at the same price (₹60 per litre), a profit of 20% was made, then the amount of pure milk in the mixture is:

25 litres

Let the amount of pure milk be x litres

then cost of milk = 60 x

After adding 5 liters of water = x + 5 litres

Selling price of mixture @ 60(x+5) = 60x + 300

gain = 300, gain % = 20

$C.P=(\frac{100}{100+gain %}).S.P$

$⇒60x=(\frac{100}{100+20}).(60x+300)$

$⇒60x=\frac{100}{120}×(60x+300)$

⇒ 60x + 300 = 72x

⇒ 12x = 300

⇒ x = $\frac{300}{12}$ = 25 litres