A mixture of milk and water measures 60 litres. It contains 10% water. How much water should be added to it, so that the water may be 25%?

12 litres

Total quantity of mixture = 60 litres,

⇒ 10 % is water and rest is milk, therefore,

⇒ Milk = 54 and Water = 6 ltr,

⇒ Amount of water to be added to make it 25%, Mil and water should be in ratio, 3 : 1,

⇒ 3x = 54,

⇒ x =18,

So, water required to make it 25% is 18 - 6 = 12 litres.