Question 1188514
<br>
Here is a quick and easy way to solve this kind of problem informally, if a formal algebraic solution is not required.<br>
(1) Consider the three percentages 30, 50, and 80 on a number line and observe/calculate that 50 is 20/50 = 2/5 of the way from 30 to 80.
(2) That means 2/5 of the mixture needs to be the higher percentage ingredient.<br>
ANSWER: 2/5 of 7 liters, or 2.8 liters, of the 80% solution; the other 4.2 liters of 30% solution.<br>
CHECK:
0.80(2.8)+0.30(4.2)=2.24+1.26=3.50
0.50(7)=3.50<br>