Question

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

Answer 1

Originally the solution was 1125 litres with acid = 45% = 506.25litres

Water content = 1125 -506.25 = 618.75 litres.

Let x litres of water be added

Then acid content would be the same 506.25 but total solution would have volume as 1125 +x litres.

Now new percentage of acid = $25<\frac{506.25}{1125+x} <30$

Simplify this to get

0.25(1125+x)<506.25<0.30(1125+x)

281.25+0.25x<506.25<337.5+0.3x

Or x<900 and x >562.50

Between 562.5 litres and 900 litres of water should be added so that the resulting will be contain more than 25 percent but less than 30 percent acid content