Question 1156055
<br>
Let x = liters of 40% acid
then 2x = liters of 85% acid  (twice as much as the 40%)
and 72-3x = liters of 25% acid  (the rest to make a total of 72 liters)<br>
The acid in those three equals 55% of the total 72 liters:<br>
{{{.40(x)+.85(2x)+.25(72-3x) = .55(72)}}}<br>
{{{.40x+1.70x+18-.75x = 39.6}}}
{{{1.35x = 21.6}}}
{{{x=16}}}<br>
ANSWER:
40% acid: x = 16 liters
85% acid: 2x = 32 liters
25% acid: 72-3x = 24 liters<br>
CHECK:
.40(16)+.85(32)+.25(24) = 6.4+27.2+6 = 39.6<br>