Sure, I’ll help solve the problems from the uploaded images using the structure "diketahui" (given), "ditanya" (asked), and "jawab" (solution). Let's go through each visible question.

Image 1

Problem 8:

• Diketahui:
  • Sudut pusat lingkaran = $60^\circ$
  • Jari-jari lingkaran = 21 cm
• Ditanya: Panjang busur lingkaran
• Jawab:
  • Rumus panjang busur lingkaran: $L = \frac{\theta}{360^\circ} \times 2 \pi r$
  • Substitute values: $L = \frac{60^\circ}{360^\circ} \times 2 \pi \times 21$
  • Simplify: $L = \frac{1}{6} \times 2 \pi \times 21 = 22 \text{ cm}$
  • Jawaban: E. 22 cm

Problem 9:

• Diketahui:
  • Jari-jari lingkaran = 3 m
• Ditanya: Panjang garis putih yang membentuk lingkaran (keliling)
• Jawab:
  • Rumus keliling lingkaran: $K = 2 \pi r$
  • Substitute values: $K = 2 \pi \times 3 = 6 \pi \approx 18.8 \text{ m}$
  • Jawaban: D. 18.8 m

Problem 10:

• Diketahui:
  • Sudut pusat $\angle PTR = 120^\circ$
• Ditanya: Nilai $\beta$
• Jawab:
  • Karena sudut pusat adalah $120^\circ$, maka sudut keliling yang bersesuaian ($\beta$) adalah setengah dari sudut pusat.
  • $\beta = \frac{120^\circ}{2} = 60^\circ$
  • Jawaban: E. 60°

Image 2

Problem 4:

• Diketahui:
  • Jari-jari lingkaran = 21 cm
  • Sudut pusat $\angle ACB = 120^\circ$
• Ditanya: Panjang busur $\text{ACB}$
• Jawab:
  • Rumus panjang busur: $L = \frac{\theta}{360^\circ} \times 2 \pi r$
  • Substitute values: $L = \frac{120^\circ}{360^\circ} \times 2 \pi \times 21$
  • Simplify: $L = \frac{1}{3} \times 2 \pi \times 21 = 44 \text{ cm}$
  • Jawaban: B. 44 cm

Problem 5:

• Diketahui:
  • Jari-jari lingkaran $M = 7$ cm
  • Panjang busur $PQ = 9.6$ cm
• Ditanya: Besar sudut $PMQ$
• Jawab:
  • Rumus panjang busur lingkaran: $L = \frac{\theta}{360^\circ} \times 2 \pi r$
  • Substitute values and solve for $\theta$: $9.6 = \frac{\theta}{360^\circ} \times 2 \pi \times 7$
  • Simplify: $\theta = \frac{9.6 \times 360^\circ}{2 \pi \times 7} \approx 78^\circ$
  • Jawaban: D. 80°

If you need further assistance or if you have questions about other specific problems on the page, please let me know. Here are some related questions for practice:

1. What would be the length of an arc if the radius is doubled but the central angle remains the same?
2. How do you calculate the circumference of a circle with a radius of 10 cm?
3. If the radius is halved, how does the length of the arc change for a fixed angle?
4. What formula relates the area of a sector to its central angle?
5. How would you find the angle if only the arc length and radius are given?

Tip: Remember, when calculating the length of an arc, it’s helpful to convert the angle to radians for simpler calculations in more advanced math contexts.