How many gallons of a 90% antifreeze solution must be mixed with 60 gallons of 25% antifreeze to get a mixture that is 80% antifreeze?

Answer 1

Let N = gallons of 90% antifreeze

.9N + .25(60) = .8(N+60)

.9N-.8N = 48-15 = 33

.1N = 33

N = 330 gallons of 90% solution mixed with 60 gallons of 25% gives 390 gallons of 80% solution