To 100 g of a 15% sulfuric acid solution was added 150 g of its 40% solution. Determine the mass fraction

To 100 g of a 15% sulfuric acid solution was added 150 g of its 40% solution. Determine the mass fraction of sulfuric acid in its new solution.

Sulfuric acid has the formula H2SO4.
Working formula: W = (mr.v – wa / mr – pa) * 100%.
Progress in solving the problem:
1) Calculation of the mass of the solute of the 1st solution.
2) Calculation of the mass of the solute of the 2nd solution.
3) Calculation of the mass of the solute after merging the two solutions.
4) Calculation of the mass of solutions after draining.
5) Calculation of the mass fraction of acid in the resulting solution.
Solution:
1) 100 * 15/100 = 15g.
2) 150 * 40/100 = 15g.
3) 15 + 15 = 30g.
4) 100 + 150 = 250g.
5) 30/250 * 100 = 12% – the answer.