Question 842113
Let D = density of 30% sulfuric acid

Water is 1.00 g/ml density
Let v = volume of water in milliliters to add


This equation is expecting percents are in weight per wieght:  {{{(0.30(20000)D)/(v*1+20000*D)=0.15}}}
Assumption that volumes are simply additive was made.
Solve for v and then use:

Density of 30% sulphuric acid is 1.2212 g/ml