A shopkeeper expects a gain of $$22\frac{1}{2}$$% on his cost price. If in a week, his sale was of Rs. 392, what was his profit ?

$$\eqalign{ & {\text{C}}{\text{.P}}{\text{. = Rs}}.\left( {\frac{{100}}{{122.50}} \times 392} \right) \cr & \,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}.\left( {\frac{{1000}}{{1225}} \times 392} \right) \cr & \,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}320. \cr & \therefore {\text{Profit}} = {\text{Rs}}.\left( {392 - 320} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}72 \cr} $$