How much water must be added to a cask which contains 30 liters of milk at the cost price of Rs 5 li...........

Explanation:

This question can be solved in so many different ways.
But the method of alligation method is the simplest of
all the methods. We will apply the alligation on the price
of milk, water, and mixture.
Therefore , ratio of milk and water should be = 5 – 3 / 3-0 = 2/3
Thus, added water = 30×3/2
= 45 liters