How much water must be evaporated from 10 gal of a 12% sugar solution in order to obtain a 15% sugar solution?

Question

I don't understand the water part.

Answer 1

you set up a proportion

 

if the concentration goes up from 12% to 15%, then the amount of water must go down from 10 gallons to x gallons.

 

12/15 = x/10

 

x = 10(12/15) = 8 gallons

 

Therefore you must evaporate 2 gallons to leave you with 8 gallons