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 = ?

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
$$\eqalign{ & {\text{Profit}}\% = \frac{{100}}{{900}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 11\frac{1}{9}\% \cr} $$