Question 225811
The radiator of Mark's 2003 Chevrolet holds 16 quarts. It is now filled with 20% antifreeze solution. How many quarts must Mark drain and replace with pure antifreeze for the radiator to contain a 50% antifreeze solution? 
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Let x = amount drained and replaced with 100% antifreeze
then
16-x = amount of 20% antifreeze solution
.
.20(16-x) + x = .50(16)
3.2-.20x + x = 8
3.2+ .8x = 8
.8x = 4.8
x = 6 quarts