A shopkeeper sells rice at 10% profit and uses weight 30% less the actual measure. His gain percent is = ?

Answer: Option B

Let CP of 1 kg. of rice be Rs. 100
As he uses 30% less weight
∴ SP of 700 gm. of rice = Rs. 110
∴ SP of 100 gm. of rice
$$\begin{array}{rl}& =\frac{110}{700}\times 1000\\ & =\frac{1100}{7}\\ & =157\frac{1}{7}\\ & \therefore \text{Profit}\%=57\frac{1}{7}\%\end{array}$$