SOLUTION: A 6-quarts radiator contains a 20% antifreeze solution. How much of the solution needs to be drained out and replaced with pure antifreeze in order to raise the solution to 60% ant

Question 102651: A 6-quarts radiator contains a 20% antifreeze solution. How much of the solution needs to be drained out and replaced with pure antifreeze in order to raise the solution to 60% antifreeze?
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
Tricky question.
We have to figure out what mixture of pure antifreeze must be mixed with 20% antifreeze to give a 60% soln.
let x be the amount of 20% (.2) soln and 6-x be the amount of 100% (1) antifreeze.
In 6 quarts of 60% antifreeze is 3.6 quarts of pure antifreeze.
.2x+6-x=3.6
-.8x+6=3.6
-.8x=-2.4
x=3
So 3 quarts need to be drained out and replaced with 3 quarts of 100% antifreeze.
Ed
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