SOLUTION: How many quarts of an 80% alcohol solution must be added to 10 quarts of a 50% alcohol solution to give a 70% solution?

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Question 1172280: How many quarts of an 80% alcohol solution must be added to 10 quarts of a 50% alcohol solution to give a 70% solution?
Found 3 solutions by josgarithmetic, MathTherapy, greenestamps:
Answer by josgarithmetic(39617) About Me  (Show Source):
Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

How many quarts of an 80% alcohol solution must be added to 10 quarts of a 50% alcohol solution to give a 70% solution?
He's WRONG, again.

The amount needed is NOT 2 quarts, and so, cross%28Q=2%29

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


A solution without formal algebra....

(1) 70% is 2/3 of the way from 50% to 80% (picture the three percentages on a number line....)

(2) That means 2/3 of the mixture is the 80% solution.

So the 10 quarts of the 50% solution is 1/3 of the mixture; and that means the 2/3 of the mixture is 20 quarts.

ANSWER: 20 quarts