Shoe Size Angle
1. **State the problem:** We have shoe size frequencies for sizes 4, 5, and 6 from a total of 40 people. The frequencies for sizes 4 and 6 are 20 and 7 respectively, but the frequency for size 5 is missing. We need to find the central angle of the pie chart section representing shoe size 5.
2. **Find the missing frequency:** The total frequency is 40. Given frequencies are:
- Size 4: 20
- Size 6: 7
- Size 5: unknown, call it $x$
The sum of frequencies must be 40:
$$20 + x + 7 = 40$$
3. **Solve for $x$:**
$$x = 40 - 20 - 7 = 13$$
4. **Calculate the central angle for size 5:**
The central angle in a pie chart is proportional to the frequency:
$$\text{Central angle} = \frac{\text{Frequency}}{\text{Total frequency}} \times 360^\circ$$
For size 5:
$$\frac{13}{40} \times 360^\circ = 117^\circ$$
**Final answer:** The central angle for shoe size 5 is $117^\circ$.