A dishonest dealer claims to sell a product at its cost price. He uses a counterfeit weight that is 20% less than the real weight and also added 10% impurities to the product. Find the net profit % of the dealer.

37.50%

                 CP     :     SP

20%   →    80     :     100

10%  →     10     :     11

            ---------      -------

                  8            11

Profit = \(\frac{3}{8}\) × 100

        = 37.50%