Which of the following statements are correct?
A. A man purchased an item at 4/5​ of its selling price ‘X’, and sold it at 5% more than ‘X’. His gain is 25%.
B. A dealer professes to sell his goods at cost price but uses a weight of 900g for a kg weight. His gain is 11 1/9%.
C. If loss is one third of the selling price, the loss percentage is 25%.
D. By selling 100 pens, a vendor gains the selling price of 20 pens. His gain is 20%. Choose the correct answer from the options given below: