SOLUTION: How many gallons of 50% antifreeze solution must be mixed with 70 gallons of 25% antifreeze to get a mixture that is 40% antifreeze?

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Question 215529: How many gallons of 50% antifreeze solution must be mixed with 70 gallons of 25% antifreeze to get a mixture that is 40% antifreeze?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
How many gallons of 50% antifreeze solution must be mixed with 70 gallons of 25% antifreeze to get a mixture that is 40% antifreeze?
.
Let x = amount of 50% antifreeze added
then
.50x + .25(70) = .40(70 + x)
.50x + 17.5 = 28 + .40x
.50x = 10.5 + .40x
.10x = 10.5
x = 10.5/.10
x = 105 gallons