Question 1146352
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Here is a faster and easier way to find the answer to "mixture" problems like this.<br>
(1) The target 28% is 1/5 of the way from 20% to 60%.  (20 to 60 is a difference of 40; 20 to 28 is a difference of 8; 8/40 = 1/5.)
(2) That means 1/5 of the mixture should be the higher (60%) ingredient.<br>
ANSWER: 1/5 of 25L, or 5L, of 60% acid; the other 20L of 20% acid.