By selling an article at some price, a man gains 10% . If the article is sold at twice of the price, the gain percent will be -

$$\eqalign{ & {\text{Let C}}{\text{.P}}{\text{.}} = {\text{Rs}}.\,x. \cr & {\text{Then,}} \cr & {\text{S}}{\text{.P}}{\text{.}} = 110\% {\text{ of Rs}}.\,x. \cr & = {\text{Rs}}.\frac{{11x}}{{10}} \cr & {\text{New S}}{\text{.P}}{\text{.}} = {\text{Rs}}.\left( {2 \times \frac{{11x}}{{10}}} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}.\frac{{11x}}{5} \cr & {\text{Gain}} = {\text{Rs}}.\left( {\frac{{11x}}{5} - x} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}.\frac{{6x}}{5} \cr & \therefore {\text{Gain}}\% = \left( {\frac{{6x}}{5} \times \frac{1}{x} \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 120\% \cr} $$