Question

How much water must be evaporated from 130 gallons of a 9% acid solution to make a 12% acid solution?

Answer 1

Answer: 33 gallons

Step-by-step explanation:

We initially have 130 gallons of a $9\%$ acid solution and we need to change it to a $12\%$ acid solution, and for that it is necessary to evaporate $n$ gallons of water.

So, this situation can be mathemtically expressed as follows:

$(130)(9\%)=(130-n)(12\%)$

Then:

$(130)(\frac{9}{100})=(130-n)(1\frac{12}{100})$

Isolating $n$:

$11.7=15.6-0.12 n$

$n=32.5 \approx 33$

Hence, we need to evaporate 33 gallons of water.