SOLUTION: A chmistry student needs 10L of a 12% acid solution. The laboratory has an ample amounts of 10% and 20% acid solutions. How many liters of each solution should the student mix?

You can put this solution on YOUR website!
mixture questions are all about BEFORE and AFTER...they have to be equal.

Let x=amount of 10% acid to be added.
and so how much of the 20% acid? Leap of faith... it is everything else of the 10litres of the final amount surely? so (10-x)litres of the 20% acid.

--> 0.10*x + 0.20(10-x) is everything before mixing.

After mixing, we have 10 litres of a 12% acid --> 0.12*10

so 0.10*x + 0.20(10-x) = 0.12*10
0.1x + 2 - 0.2x = 1.2
-0.1x + 2 = 1.2
-0.1x = -0.8
x = -0.8/-0.1
x = 8 litres

and so we need 8 litres of the 10% acid and 2 litres of the 20% acid.

Easy? :-)

jon.