Question 25921
OK, first define what you need.


Let x = volume of 5% acid.


Now for the leap of faith part...how much of the pure acid is needed? Answer is (60-x)! This is the hardest part done now.


Now for the solution.
BEFORE = AFTER


0.05x + 1.00(60-x) = 0.15*60
0.05x + 60 - x = 9
-0.95x = -51
--> x = -51/-0.95
x = 53.68 fl.oz (to 2 dp)


so we need 53.68 fl.oz of the 5% acid and we will need 6.32 fl.oz of the pure acid too.


jon.