SOLUTION: How many quarts of pure antifreeze must be added to 4 quarts of a 40% antifreeze solution to obtain a 60% antifreeze solution?

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Question 877598: How many quarts of pure antifreeze must be added to 4 quarts of a 40% antifreeze solution to obtain a 60% antifreeze solution?
Answer by jim_thompson5910(35256) (Show Source):
You can put this solution on YOUR website!
"4 quarts of a 40% antifreeze solution" ---> 4*0.40 = 1.6 quarts of pure antifreeze.

Adding some unknown amount, call it x, of pure antifreeze gives you 1.6+x quarts of pure antifreeze.

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You have 4 quarts of a mixed solution and you're adding x quarts of pure antifreeze to the mix.
So you end up with a total of 4+x quarts of mixed solution.

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(amount of pure antifreeze)/(amount of solution) = percent of antifreeze

(1.6 + x)/(4 + x) = 0.60

1.6 + x = 0.60(4 + x)

1.6 + x = 0.60(4) + 0.60(x)

1.6 + x = 2.4 + 0.60x

1.6 + x - 0.60x = 2.4

x - 0.60x = 2.4 - 1.6

0.40x = 0.8

x = 0.8/0.40

x = 2

You need to add 2 quarts of pure antifreeze.