Determine the mass fraction of sodium chloride obtained by mixing two solutions of sodium

Determine the mass fraction of sodium chloride obtained by mixing two solutions of sodium chloride: 120 g in mass with 40% mass fraction of NaCl and 200 g in mass with 15% NaCl mass fraction.

Find the mass of sodium chloride in the first solution:
120 * 0.4 = 48 grams;

Find the mass of pure sodium chloride in the second solution:
200 * 0.15 = 30 grams;

Find the mass of pure sodium chloride in the resulting solution:
48 + 30 = 78 grams;

Let’s find the mass of the resulting solution:
200 + 120 = 320 grams;

Let’s find the mass fraction of sodium chloride in the resulting solution:
78/320 = 0.24375 (24.375%);

Answer: the mass fraction of sodium chloride in the resulting solution is 24.375%.