A solution is obtained by mixing $$200\,g$$  of $$30\% $$  and $$300\,g$$  of $$20\% $$  solution by weight. What is the percentage of solute in the final solution ?

Solution :
Solute in $$200\,g$$  of $$30\% $$  solution $$ = 60\,g$$
Solute in $$300\,g$$  of $$20\% $$  solution $$ = 60\,g$$
Total grams of solute $$ = 120\,g$$
Total grams of solution $$ = 200 + 300 = 500\,g$$
$$\% $$  of solute in the final solution $$ = \frac{{120}}{{500}} \times 100 = 24\% $$