Determine the mass of salt contained in 380g of a 40% solution.

Explanation of the solution to the problem: the basic formula for the calculation:
w = m (r.v.) / m (r-ra) * 100%, where w is the mass fraction of the solute, m (r.v.) is the mass of the solute, m (r-ra) is the mass of the solution. Therefore, the mass of the solute is calculated by the formula: m (r.v.) = M (r-ra) * w, where w is expressed in fractions. Substituting the data from the condition, we get: m (r.v.) = M (r-ra) * w = 380 * 0.4 = 152 g.