Ratio of milk to water in a container 'P' is 2:3 whereas ratio of milk to water in container 'Q' is 3:7. Find the quantity of 'Q' that must be added to 250 litres of 'P' so that ratio of milk to water in the resultant mixture will be 29:51.

Quantity of milk in 250 litres of 'P' = (2/5) × 250 = 100 litres

Quantity of water in 250 litres of 'P' = (3/5) × 250 = 150 litres

Let the quantity of 'Q' added be '10m' litres

Quantity of milk added from 'Q' = (3/10) × 10m = 3m litres

Quantity of water added from 'Q' = (7/10) × 10m = 7m litres

So, (100 + 3m) : (150 + 7m) = 29 : 51

Or, 51 × (100 + 3m) = 29 × (150 + 7m)

Or, 5100 + 153m = 4350 + 203m

Or, 50m = 750

Or, m = 15

Therefore, required quantity = 10 × 15 = 150 litres