https://file.aiquickdraw.com/mathbot/file/1730179108027gq45pf3u.jpg

Keliling bangun di bawah ini adalah ....
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10 points

44 cm
88 cm
72 cm
86 cm

To calculate the perimeter (or "keliling") of the half-circle in the image, we need to account for both the curved edge and the straight diameter.

Given:
- Diameter \( d = 28 \, \text{cm} \)
- Radius \( r = \frac{d}{2} = \frac{28}{2} = 14 \, \text{cm} \)

### Steps:
1. **Calculate the curved part (half the circumference of a circle):**

   The formula for the circumference of a full circle is:
   \[
   C = 2 \pi r
   \]

   For a half-circle, the curved part is:
   \[
   \text{Curved part} = \pi r = \pi \times 14 = 44 \, \text{cm} \quad (\text{approx})
   \]

2. **Add the straight part (diameter):**

   \[
   \text{Total perimeter} = \text{Curved part} + d = 44 + 28 = 72 \, \text{cm}
   \]

### Answer:
The perimeter of the shape is **72 cm**.

Would you like further explanation on any part?

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### Related Questions:
1. What would be the perimeter if the diameter were doubled?
2. How would the area of this half-circle be calculated?
3. If only the curved part is measured, what would its length be?
4. How does changing the radius affect the perimeter?
5. How would you find the perimeter of a quarter-circle with the same radius?

### Tip:
Remember, for semicircles, add both the half-circumference and the diameter to get the total perimeter.

Find the perimeter of a semicircle with a 28 cm diameter by calculating the half-circumference and adding the diameter. This solution is ideal for Grades 6-8 students learning about perimeter and composite shapes.

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