The ratio of milk and water in the resultant mixture is 9 : 1.

Sum ofthe ratio = 3 +2 = 5

Amount of milk in the mixture = 20 $\times \frac{3}{5}$ = 12 litre

Amount of water in the mixture = 20$\times \frac{2}{5}$ = 8 litre

After removal of 10 litre mixture, the amount of milk will be = 10$\times \frac{3}{5}$= 6 litres

& After removal of 10 litre mixture, the amount of water will be = 10$\times \frac{2}{5}$ = 4 litres

After pouring 10 litre pure milk, the amount of milk in the new mixture will be = 10 +6 = 16 litres

& the amount of water will remain unchanged, that is 4 litres.

Now the ratio of milk & water in the new mixture will be = 16 : 4 = 4 : 1

After removal of 10 litre mixture, the amount of milk in that mixture will be = 10$\times \frac{4}{5}$= 8 litres

And the amount of water will be = 10$\times \frac{1}{5}$= 2 litres

Now, After addition of 10 litre pure milk in the mixture, the new amount of milk and water will

be (8 + 10) = 18 litres and 2 litres respectively.

The ratio of milk and water in the resultant mixture = 18 : 2 = 9 : 1.