SOLUTION: The capacity of a car radiator is 18 quarts. If it is full of a 20% antifreeze solution, how many quarts must be drained off and replaced by a 100% solution to give 18 quarts of a

Question 321483: The capacity of a car radiator is 18 quarts. If it is full of a 20% antifreeze solution, how many quarts must be drained off and replaced by a 100% solution to give 18 quarts of a 39% solution?
Answer by galactus(183) (Show Source): You can put this solution on YOUR website!
Let x=amount being drained.
Original 20% mixture minus amount drained is .20(18-x).
Pure antifreeze added back is x.
New 39% mixture is .39(18)
So, we solve the equation
.20(18-x)+x=.39(18)
x=4.275 quarts should be drained and replaced with pure antifreeze.

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