1. **Problem 1: Calculate the discount and sale price for a knapsack originally priced at 2500 with a 20% discount.** Step 1: Calculate the discount amount. The formula for discount $D$ is: $$D = \text{Original Price} \times \text{Discount Rate}$$ Substitute the values: $$D = 2500 \times 0.20 = 500$$ Step 2: Calculate the sale price. The sale price $SP$ is the original price minus the discount: $$SP = 2500 - 500 = 2000$$ Step 3: Conclusion. The discount on the knapsack is 500 and the sale price is 2000. 2. **Problem 2: Find the rate of discount when the original price of a microwave oven is 8900 and the discount amount is 445.** Step 1: Calculate the sale price. Sale price is: $$SP = 8900 - 445 = 8455$$ Step 2: Calculate the discount rate. Discount rate $r$ is given by: $$r = \left(\frac{\text{Discount}}{\text{Original Price}}\right) \times 100 = \left(\frac{445}{8900}\right) \times 100$$ Calculate: $$r = 0.05 \times 100 = 5\%$$ Step 3: Conclusion. The sale price of the microwave oven is 8455 and the discount rate is 5%.