Question 1184009
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A classic formal algebraic solution would go something like this....<br>
You are mixing 5 quarts that is 30% antifreeze and x quarts that are 100% antifreeze to get (5+x) quarts that is 50% antifreeze:<br>
{{{.30(5)+1.00(x)=.50(5+x)}}}
{{{1.5+x=2.5+.5x}}}
{{{.5x=1}}}
{{{x=1/.5=2}}}<br>
ANSWER: 2 quarts<br>
An informal method that will give you the answer within 15 seconds if you understand it....<br>
(1) Look at the three percentages 30, 50, and 100 on a number line and observe/calculate that 50 is 2/7 of the way from 30 to 100.  (30 to 100 is a difference of 70; 30 to 50 is a difference of 20; 20/70 = 2/7.)
(2)That means 2/7 of the mixture is the 100% antifreeze that you are adding.
(3) So the 5 quarts you started with is 5/7 of the mixture; that means 2/7 of the mixture is 2 quarts.<br>
ANSWER: 2 quarts<br>