SOLUTION: How many quarts of pure antifreeze must be added to 9 quarts of a 40% antifreeze solution to obtain a 60% antifreeze solution?

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Question 486085: How many quarts of pure antifreeze must be added to 9 quarts of a 40% antifreeze solution to obtain a 60% antifreeze solution?
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
1n+.4(9)=.6(n+9)
n+3.6=.6n+5.4
.4n=1.8
n=1.8/.4=4.5
4.5 quarts of pure antifreeze must be added to make 13.5 quarts of 60% antifreeze..