Expert: Scott A Wilson - 10/28/2009

Question
Grace dilutes 4.8 fluid oz. of pure hydrogen peroxide with 27.2 fluid oz. of water to make 32 fluid oz. of a 22% hydrogen peroxide bleaching solution. how much of the bleaching solution should be replaced by pure hydrogen peroxide?

Answer
Currently, we have 4.8/32 = 24/160 = 3/20 = 15/100 = 15%
as the concentration of hydrogen peroxide.

We want it to be 22%.

Take X as the fraction of added solution and (1-X) as the mixed.

This results in X + 0.15(1-X) = 0.22.
This means that 0.85X = 0.22 - 0.15
Dividing by 0.85 gives X = 0.07/0.85.

This gives X = 0.082352941, according to Excel.
Sice this is as 32 oz container, we take that times 32 to get ounces.
In other words, replace 2.635294118 oz, which is almost 2 2/3.