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To solve this problem, we need to find the circumference (perimeter) of the shaded area, which is the annular sector formed between two concentric circular sectors. Here’s how to approach it:

### Given:
1. Outer radius (\(R\)) = 14 cm
2. Inner radius (\(r\)) = 7 cm
3. Central angle (\(\theta\)) = \(72^\circ\)
4. \(\pi = \frac{22}{7}\)

### Steps to Solve:

#### 1. Calculate the Arc Lengths of Both Sectors

For a sector with a central angle \(\theta\), the arc length \(L\) is given by:
\[
L = \frac{\theta}{360^\circ} \times 2\pi \times \text{radius}
\]

**Arc Length of Outer Sector** (\(L_{\text{outer}}\)):
\[
L_{\text{outer}} = \frac{72^\circ}{360^\circ} \times 2 \times \frac{22}{7} \times 14
\]
Simplify this:
\[
L_{\text{outer}} = \frac{1}{5} \times 2 \times \frac{22}{7} \times 14 = \frac{1}{5} \times 88 = 17.6 \, \text{cm}
\]

**Arc Length of Inner Sector** (\(L_{\text{inner}}\)):
\[
L_{\text{inner}} = \frac{72^\circ}{360^\circ} \times 2 \times \frac{22}{7} \times 7
\]
Simplify this:
\[
L_{\text{inner}} = \frac{1}{5} \times 2 \times \frac{22}{7} \times 7 = \frac{1}{5} \times 44 = 8.8 \, \text{cm}
\]

#### 2. Calculate the Total Perimeter of the Shaded Area

The total perimeter of the shaded area includes:
- The outer arc length (\(L_{\text{outer}}\))
- The inner arc length (\(L_{\text{inner}}\))
- The two radii connecting these arcs (each with length \(14 - 7 = 7\) cm).

Thus, the total perimeter \(P\) is:
\[
P = L_{\text{outer}} + L_{\text{inner}} + 2 \times (R - r)
\]
Substitute the values:
\[
P = 17.6 + 8.8 + 2 \times 7
\]
\[
P = 17.6 + 8.8 + 14 = 40.4 \, \text{cm}
\]

### Answer:
The perimeter of the shaded area is **40.4 cm**.

Would you like further details or have any questions?

### Related Questions:
1. How would the solution change if the central angle were different?
2. What is the area of the shaded region between the two sectors?
3. How would you calculate the perimeter if the inner radius were 10 cm instead?
4. How does the arc length formula derive from the general circumference formula?
5. Can you calculate the circumference of a full circle with radius 14 cm?

### Tip:
Always check if there is a specific value given for \(\pi\) in problems. Using the assigned value ensures accuracy and avoids discrepancies in answers.

Perhatikan gambar! Jika π = 22/7, maka keliling daerah yang diarsir adalah...

Learn how to find the perimeter of a shaded annular sector with a central angle of 72°, outer radius of 14 cm, and inner radius of 7 cm, using π = 22/7. This solution covers arc length calculation and sector perimeter, suitable for high school geometry students.

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