30 mL of a 40% acid solution in a test tube. How much of the solution should be poured off and replaced with pure acid so that the new mixture is 70% acid?

Question

its trig/precalc

Answer 1

Hello,

Let's convert percentage into decimals and assume the amount of the solution poured off and replaced with pure acid is x. The following linear equation provides the solution for x:

(30-x)*0.4 + x = 30*0.7

in a simplified form

0.6x + 12 = 21

This linear equation can be solved either manually or by using online Linear Equation Solver (http://examn8.com/LinearEquations.aspx)

The answer is: x=15 ml

Hope this may help.