To 80 g of a 20% salt solution, another 20 g of the same salt was added. Determine the mass fraction

To 80 g of a 20% salt solution, another 20 g of the same salt was added. Determine the mass fraction of salt in the new solution.

Progress in solving the problem:
1) Calculation of the mass of the solute of the salt in its solution.
2) Calculation of the mass of the solute after adding 20 g of the same salt.
3) Calculation of the mass of the solution after adding 20 g of salt.
4) Calculation of the mass fraction of the substance in the resulting solution.
Solution:
1) In order to find the mass of a solute, we must multiply the mass fraction of the substance by the mass of the solution and divide by one hundred percent: 80 * 20/100 = 16g.
Because salt is added, then both the mass of the solute and the mass of the solution itself change.
2) 16 + 20 = 36g.
3) 80 + 20 = 100g.
4) W = 36/100 * 100 = 36% – the answer.