A shopkeeper claims to sell his articles at Rs. 20 per kg which cost him Rs. 23 per kg. But while selling, he uses a false weight and gives only 800 gm instead of 1 kg. What is his profit percentage?

$$\eqalign{ & \frac{{{\text{Sale Price}}}}{{{\text{Cost Price}}}} = \frac{{20}}{{23}} \times \frac{{1000}}{{800}} = \frac{{50}}{{46}} \cr & {\text{Cost Price}} = 46 \cr & {\text{Sale Price}} = 50 \cr & {\text{Profit }}\% = \frac{4}{{46}} \times 100 = 8\frac{{16}}{{23}}\% \cr} $$