1. **State the problem:** Darell buys a whistle for 0.33 that originally cost 0.50. We need to find the percentage discount. 2. **Formula for percentage discount:** $$\text{Discount Percentage} = \left(\frac{\text{Original Price} - \text{Sale Price}}{\text{Original Price}}\right) \times 100\%$$ 3. **Calculate the discount amount:** $$0.50 - 0.33 = 0.17$$ 4. **Apply the formula:** $$\text{Discount Percentage} = \left(\frac{0.17}{0.50}\right) \times 100\%$$ 5. **Simplify the fraction:** $$\frac{0.17}{0.50} = \frac{\cancel{0.17}}{\cancel{0.50}} = 0.34$$ 6. **Calculate the percentage:** $$0.34 \times 100\% = 34\%$$ **Final answer:** Darell received a 34% discount on the whistle.