1. **State the problem:** You sold 400 products last week and 600 products this week. We want to find the percentage improvement in sales. 2. **Formula:** The percentage improvement is given by $$\text{Percentage Improvement} = \frac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100$$ 3. **Apply the values:** $$\text{Percentage Improvement} = \frac{600 - 400}{400} \times 100$$ 4. **Calculate the difference:** $$\frac{200}{400} \times 100$$ 5. **Simplify the fraction:** $$\frac{\cancel{200}}{\cancel{400}} \times 100 = \frac{1}{2} \times 100$$ 6. **Calculate the final percentage:** $$\frac{1}{2} \times 100 = 50$$ **Answer:** You improved your sales by 50%.