By selling an article for Rs. 100 a man gains Rs.15. Then, his gain % is -

$$\eqalign{ & {\text{S}}{\text{.P}}{\text{.}} = {\text{Rs}}{\text{. }}100 \cr & {\text{Gain}} = {\text{Rs}}{\text{. }}15. \cr & \therefore {\text{C}}{\text{.P}}{\text{.}} = {\text{Rs}}.\left( {100 - 15} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}85 \cr & {\text{Gain }}\% = \left( {\frac{{15}}{{85}} \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{300}}{{17}}\% \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 17\frac{{11}}{{17}}\% \cr} $$