There are two buckets X and Y containing mixture of milk and water in which concentration of milk is (a-9)% and (a+15)%, respectively. They are mixed together in a fixed ratio to get 64 litres of mixture of (a+12)% milk concentration. Find the amount of mixture used from bucket X.
Ratio = 3: 21 = 1: 7 Therefore, required amount of mixture used from bucket X = (1/8)× 64 = 8 litres.