Question 1153358
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If an algebraic solution is not required, here is a common sense method that will get you to the answer much faster than algebra.<br>
(1) Use any number of different kinds of calculations to determine that the target 70% is "twice as close to 80% as it is to 50%"<br>
(2) Therefore, the amount of the 80% ingredient must be twice the amount of the 50% ingredient.<br>
(3) Since there are 10 liters of the 80% solution, there must be 5 liters of the 50% solution.<br>
ANSWER: 5 liters<br>