Question

How many litres of water will have to be added to 1125 litres of the 45% solution of acid so that the resulting mixture will contain more than 25% but less than 30% acid content?

Answer 1

Let x litres of water is required to be added. Then, total mixture = (x + 1125) litres It is evident that the amount of acid contained in the resulting mixture is 45% of 1125 litres. 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 

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

Thus, the required number of litres of water that is to be added will have to be more than 562.5 but less than 900.