A mixture of 20% disinfectant solution is to be made from 13% and 23% disinfectant solution. How much of each solution should be used if 40 gallons of the 20% solution are needed?

Answer 1

If there are x gallons of 13%, then the rest (40-x) is 23%. So, adding up all the disinfectant, you have

.13x + .23(40-x) = .20*40