1. **Problem:** A trader sold a wrist watch for 3150 after giving a 10% discount. Find the marked price of the watch. 2. **Formula:** The selling price (SP) after discount is given by $$ SP = MP \times (1 - \text{discount rate}) $$ where $MP$ is the marked price. 3. **Given:** - Selling price, $SP = 3150$ - Discount rate = 10% = 0.10 4. **Step:** Substitute the values into the formula: $$ 3150 = MP \times (1 - 0.10) $$ $$ 3150 = MP \times 0.90 $$ 5. **Step:** Solve for $MP$: $$ MP = \frac{3150}{0.90} $$ $$ MP = 3500 $$ 6. **Answer:** The marked price of the watch is **3500**.