A dishonest dealer professes to sell his goods at cost price but uses a weight of 875 gms for the kilogram weight. His gain in the percentage is = ?

Answer: Option C

Let dealer purchase 1000 gm in Rs. 1000
But at selling time sold 875 gm in place of 1000 gm
So,
$$\begin{array}{rl}& \text{Profit }\%=\frac{1000-875}{875}\times 100\\ & =14\frac{2}{7}\%\end{array}$$