1. **State the problem:** We have a pie chart with three categories. One category covers a sector angle of 120 degrees. We want to find what percentage this category represents of the whole pie chart. 2. **Formula and rules:** The total angle in a pie chart is always 360 degrees. 3. **Calculate the percentage:** The percentage represented by a sector angle is given by the formula: $$\text{Percentage} = \left(\frac{\text{Sector angle}}{360}\right) \times 100$$ 4. **Substitute the given value:** $$\text{Percentage} = \left(\frac{120}{360}\right) \times 100$$ 5. **Simplify:** $$\text{Percentage} = \left(\frac{1}{3}\right) \times 100 = 33.33\%$$ 6. **Interpretation:** The category with a sector angle of 120 degrees represents approximately 33.33% of the pie chart, not 50%.