A dishonest dealer sells the goods at 7% loss on cost price but uses 18% less weight. What is his percentage of profit? (Correct to 2 decimal places)

As, Loss (a) = 7% and Less weight (b) = 18%
Then,
$$\eqalign{ & \frac{{{\text{Profit }}\% }}{{{\text{Loss }}\% }} = \frac{{{\text{b}} \pm {\text{a}}}}{{100 - {\text{b}}}} \times 100 \cr & \Rightarrow \frac{{18 - 7}}{{100 - 18}} \times 100 \cr & \Rightarrow \frac{{11}}{{82}} \times 100 \cr & \Rightarrow 13.4146 \approx 13.41\% \cr} $$
∴ The dealer's profit % is 13.41%.