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ACS Junior 2025 P6 Maths Prelim — Paper 1 Booklet A Q12 Solution

Paper 1 Booklet A · Q12 · 2 marks · Area and Perimeter

Question

The shaded figure is made up of a large semicircle and a square with a small semicircle cut-out from the square. The diameter of the small semicircle is 10 cm, and the diameter of the large semicircle is twice the length of the diameter of the small semicircle. What is the perimeter of the shaded figure? (Take $\pi = 3.14$)
Answer: 1

Worked solution

  1. \text{Small semicircle: } d = 10,\ r = 5,\ \text{arc} = \pi \times 5 = 15.7 \text{ cm}
  2. \text{Large semicircle: } d = 20,\ r = 10,\ \text{arc} = \pi \times 10 = 31.4 \text{ cm}
  3. \text{Add the relevant straight edges from the figure}
  4. \text{Perimeter} = 77.1 \text{ cm}

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