Let x liters (l) of water is required to be added.

Then, total mixture = (x + 1125) liters

It is evident that the amount of acid CONTAINED in the RESULTING mixture is 45% of 1125 liters(l) .

This resulting mixture will contain more than 25% but less than 30% acid content.

∴30% of (1125 + x) > 45% of 1125

And, 25% of (1125 + x) < 45% of 1125

30% of (1125 + x) > 45% of 1125 

Calculations 

506.25/(1125 + x) >= .25 Solving for x we get 

506.25 >= (.25)(1125 + x) 

506.25 >= 281.25 + .25x 

225 >= .25x 

900 >= x. So we need to add 900 litres to make the WEAKER solution; this is the most we can add and still be within the range stated for the problem. 

For the stronger solution, 

506.25/(1125 + x) <= .3 

506.25 <= (1125 + x)(.3) 

506.25 <= 337.5 + .3x 

168.75 <= .3x 

562.5 <= x. So we need to add at least 562.5 litres, this will make the stronger solution. 

The final answer, then, is 562.5 <= x <= 900

Thus, the required number of liters (L) of water that is to be added will have to be more than 562.5 but less than 900