Explanation:

- Initially, the mixture contains 33.33% water and 66.67% milk.

- So, there are 60 litres of water and 120 litres of milk in the original 180 litres.

- When 54 litres of the mixture is removed:

- Water removed = 33.33% of 54 litres = 18 litres

- Milk removed = 66.67% of 54 litres = 36 litres

- Remaining amounts:

- Water left = 60 - 18 = 42 litres

- Milk left = 120 - 36 = 84 litres

- Water needs to be 25% of the new total volume:

- If water is 25%, milk should make up 75%

- Given the water left is 42 litres, the total mixture should be 42 / 0.25 = 168 litres

- Therefore, milk required = 168 - 42 = 126 litres

- Milk to be added = 126 - 84 = 42 litres

- The correct option is Option 1: 42