How many gallons of 70% antifreeze solution must be mixed with 80 gallons of 30% antifreeze to get a mixture that is 60% antifreeze?

Answer 1

Use a weighted average........ let x = unknown number of gallons of the 70% solution.

then {x(70%) + 80(30%)}/{x + 80} = 60%

Solving for x, the answer is 240 gallons!