SOLUTION: please help me with this problem of writing a rational and/or polynomial equation. If Laura mixes 5mL acetic acid with 120mL water to make a solution that should be 5% acid, how do

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Question 737199: please help me with this problem of writing a rational and/or polynomial equation. If Laura mixes 5mL acetic acid with 120mL water to make a solution that should be 5% acid, how does she know she needs to add more acetic acid?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
She has 5+120 = 125 mL of solution total when she mixes the acid and water.

5/125 = 1/25 = 0.04 = 4% of this solution is pure acid

BUT she wants 5% of the solution to be pure acid. So she needs more acetic acid to go from 4% acid to 5% acid.