Home / iGCSE Mathematics (0580) – C5.5 Compound shapes and parts of shapes- Exam Style Questions Paper 3

iGCSE Mathematics (0580) - C5.5 Compound shapes and parts of shapes- Exam Style Questions Paper 3- New Syllabus

Question

The diagram shows a garden.
The garden has a circular pond and the shaded area is grass.
The width of the grass area is equal to the diameter of the pond.

(a) Find the area of the pond.

(b) Find the area of the grass.

(c) Find the percentage of the garden that is grass.

Most-appropriate topic codes (Cambridge IGCSE Mathematics 0580):

• C5.3 Circles, arcs and sectors (a,b)
• C5.5 Compound shapes and parts of shapes (b,c)
▶️ Answer/Explanation

(a)
The diameter of the pond is $10\text{ m}$, so the radius is $5\text{ m}$. The total area of the full circular pond is:
$\text{Area} = \pi \times 5^2$
$\text{Area} \approx 78.5\text{ m}^2$
✅ Answer: 78.5

(b)
The diagram implies half of the circular pond intrudes into the rectangle, creating the grass area. First, find the total area of the $10\text{ m}$ by $16\text{ m}$ rectangle, then subtract half the area of the pond.
$\text{Area of rectangle} = 10 \times 16 = 160$
$\text{Grass Area} = 160 – (\frac{1}{2} \times 78.54)$
$\text{Grass Area} = 160 – 39.27 = 120.7\text{ m}^2$
✅ Answer: 120.7

(c)
The total area of the garden is the area of the grass plus the area of the pond inside the garden outline (the rectangle), which is exactly the area of the $10 \times 16$ rectangle.
$\text{Percentage} = (\frac{120.73}{160}) \times 100 \approx 75.5\%$
✅ Answer: 75.5

Question

The diagram shows a right-angled triangle, ABC, and a semicircle. The radius of the semicircle is 4.5 cm. AC = 8.9 cm and BC = 13.2 cm.

(a) Calculate the shaded area. Give the units of your answer.

(b) Calculate AB.

▶️ Answer/Explanation
Solution

(a) Ans: 26.9 cm²

Step 1: Calculate triangle area

Area = ½ × base × height = ½ × 8.9 × 13.2 = 58.74 cm²

Step 2: Calculate semicircle area

Area = ½ × π × r² = ½ × π × 4.5² ≈ 31.81 cm²

Step 3: Find shaded area

Shaded area = Triangle – Semicircle = 58.74 – 31.81 = 26.93 cm² ≈ 26.9 cm²

(b) Ans: 15.9 cm

Using Pythagoras’ theorem:

AB² = AC² + BC² = 8.9² + 13.2² = 79.21 + 174.24 = 253.45

AB = √253.45 ≈ 15.92 cm ≈ 15.9 cm

Key Notes:

  • The right angle is at C (implied by diagram and Pythagoras’ application)
  • All calculations shown to 2 decimal places for precision
  • Final answers rounded to 1 decimal place as typical for measurements
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