Math Problem Statement

The compound shape below is formed from a semicircle and a rectangle. Calculate the area of the compound shape. Give your answer in cm² to 1 d.p.

Solution

Let's break this problem down step by step:

Step 1: Identify the shapes

The compound shape consists of:

  1. A rectangle with dimensions:
    • Width = 4 cm
    • Height = 16 cm
  2. A semicircle with:
    • Diameter = 4 cm (same as the rectangle’s width)
    • Radius = 4 cm ÷ 2 = 2 cm

Step 2: Calculate the area of the rectangle

Area of rectangle=width×height\text{Area of rectangle} = \text{width} \times \text{height} =4×16=64 cm2= 4 \times 16 = 64 \text{ cm}^2

Step 3: Calculate the area of the semicircle

The area of a full circle is: πr2\pi r^2 Since we have a semicircle, we divide by 2: Area of semicircle=12πr2\text{Area of semicircle} = \frac{1}{2} \pi r^2 =12×π×22= \frac{1}{2} \times \pi \times 2^2 =12×π×4= \frac{1}{2} \times \pi \times 4 =4π2=2π= \frac{4\pi}{2} = 2\pi

Approximating π\pi as 3.1416: Area of semicircle2×3.1416=6.2832 cm2\text{Area of semicircle} \approx 2 \times 3.1416 = 6.2832 \text{ cm}^2

Step 4: Calculate the total area

Total Area=Area of rectangle+Area of semicircle\text{Total Area} = \text{Area of rectangle} + \text{Area of semicircle} =64+6.2832= 64 + 6.2832 =70.2832= 70.2832

Step 5: Round to 1 decimal place

70.3 cm2\mathbf{70.3 \text{ cm}^2}

Final Answer:

70.3 cm2\boxed{70.3 \text{ cm}^2}

Would you like me to explain any step further?

Related Questions:

  1. How do you find the perimeter of this compound shape?
  2. What would the total area be if the semicircle was a full circle instead?
  3. How would the area change if the width of the rectangle were doubled?
  4. What is the ratio of the semicircle’s area to the rectangle’s area?
  5. How can this problem be applied in real-world construction or design?

Tip: Always check if the given shape consists of familiar geometric figures before solving for area or perimeter!

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Math Problem Analysis

Mathematical Concepts

Geometry
Area Calculation
Compound Shapes

Formulas

Area of a rectangle = width × height
Area of a semicircle = (1/2) × π × r²

Theorems

Properties of Rectangles
Properties of Circles

Suitable Grade Level

Grades 6-8