A dishonest fruit vendor sells his goods at cost price but they uses a weight of 900 gm. for the 1 kg. weight. His gain percent is = ?

Answer: Option B

According to the question,
Shopkeeper sells his goods at cost price
Let, Cost price of 1000 gm. goods = Rs. 1000
He sold 900 gm. goods
Selling price of 900 gm. goods = Rs. 1000
Cost price of 900 gm. goods = Rs. 900
$$\begin{array}{rl}& \text{Profit}\%=\frac{100}{900}\times 100\\ & =11\frac{1}{9}\%\end{array}$$