Question 44269
Hello!
The acid percentage of the mix will be given by the formula:

(Amount of X/Total Amount)*(%acid in X) + (Amount of Y/Total Amount)*(%acid in Y)

In your case, let's call Y to the 20% acid. We know that you have 60 mL of this. Let's call X to the amount we need to add of the 5% acid.

Once we add it, the total amount will clearly by (60 + X) mL. Therefore, using the formula I gave above, we get the equation:

{{{10 = (X/(60+X))*5 + (60/(60+X))*20}}}

We now have to solve for X. Let's multiply both sides of the equation by (60+X) in order to get rid of the X's in the denominator:

{{{600 + 10X = 5X + 60*20}}}
{{{5X = 1200 - 600 = 600}}}
{{{X = 120}}}

We conclude that you need to add 120 mL of the 5% acid.


I hope this helps!
Get more answers at <a href=http://www.onlinemathanswers.com>Online Math Answers.com</a>!