48.95% (m/v)
From the question we are given;
We are required to calculate the mass volume percent of solution;
How do we calculate the mass volume percent of a solution?
Mass volume percent = (mass of solute in g/Volume of solvent in mL) 100
= (186 g ÷ 380 mL)100
= 48.95%
Therefore, the mass volume percent of a NaCl solution is 48.95% (m/v).