Answer:
4 litres
Explanation:
First, we are going to find 60% of 20 litres.
20 ×
= 12 litres
∴ Pure milk 12 litres.
Now we find 40% of 20 litres.
20 ×
= 8 litres
To find the quantity of water to be added we subtract the 8 litres from the 12 litres.
12 - 8 = 4 litres
∴ 4 litres of water should be added so that pure milk becomes 40%