Let x litres of water be added.

Then total mixture = x + 600

Amount of acid contained in the resulting mixture is 45% of 600 litres.

It is given that the resulting mixture contains more than 25% and less than 30% acid content.

Therefore,

45% of 600 > 25% of (x + 600)

And

30% of (x+600) > 45% of 600

When,

45% of 600 > 25% of (x+600)

Multiplying both the sides by 100 in above equation

>

45 × 600 > 25(x + 600)

27000 > 25x + 15500

Subtracting 15500 from both the sides in above equation

27000 – 15500 > 25x + 15500 – 15500

11500 > 25x

Dividing both the sides by 25 in above equation

460 > x

Now when,

45% of 600 < 30% of (x+600)

Multiplying both the sides by 100 in the above equation

<

45 × 600 < 30(x + 600)

27000 < 30x + 18000

Subtracting 18000 from both the sides in above equation

27000 – 18000 < 30x + 18000 – 18000

9000 < 30x

Dividing both the sides by 30 in above equation

300 < x

Thus, the amount of water required to be added ranges from 300 litres to 460 litres.