SOLUTION: how many quarts of pure antifreeze must be added to 5 quarts of 10% antifreeze solution to obtain a 30% antifreeze solution

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Question 212067: how many quarts of pure antifreeze must be added to 5 quarts of 10% antifreeze solution to obtain a 30% antifreeze solution
Answer by HyperBrain(694) About Me  (Show Source):
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Let x=the amount of pure antifreeze required
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If we add x quarts to 5 liters, we get x+5 quarts.
For x quarts of pure antifreeze, we have x quarts of antifreeze.
For 5 quarts of 10% antifreeze, we have (0.1)(5 quarts)=0.5 quart of antifreeze
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So, we have the equation,
0.3(x+5)=x+0.5
0.3x+1.5=x+0.5
0.7x=1
7x=10
x=10/7 quarts