Math Problem Statement

Find area and perimeter

Solution

The image contains a composite shape made up of a rectangle with a semicircle on top. The dimensions given are:

  • Height of the rectangle: 17 cm
  • Width of the rectangle (and the diameter of the semicircle): 28 cm

(a) Perimeter Calculation:

The perimeter of this shape consists of:

  1. The two sides of the rectangle (2 × 17 cm).
  2. The width of the rectangle (28 cm).
  3. The curved part of the semicircle (half the circumference of a full circle).

The formula for the circumference of a full circle is C=πdC = \pi d, where dd is the diameter. For the semicircle, the perimeter is half of that: Curved part of semicircle=12×π×28 cm=14π cm\text{Curved part of semicircle} = \frac{1}{2} \times \pi \times 28 \text{ cm} = 14\pi \text{ cm}

So, the total perimeter PP is: P=2×17 cm+28 cm+14π cmP = 2 \times 17 \text{ cm} + 28 \text{ cm} + 14\pi \text{ cm} P=34 cm+28 cm+14π cmP = 34 \text{ cm} + 28 \text{ cm} + 14\pi \text{ cm} P=62 cm+14π cm62 cm+43.96 cm105.96 cmP = 62 \text{ cm} + 14\pi \text{ cm} \approx 62 \text{ cm} + 43.96 \text{ cm} \approx 105.96 \text{ cm}

(b) Area Calculation:

The area of the composite shape consists of:

  1. The area of the rectangle.
  2. The area of the semicircle.

1. Area of the rectangle: Arectangle=length×width=28 cm×17 cm=476 cm2A_{\text{rectangle}} = \text{length} \times \text{width} = 28 \text{ cm} \times 17 \text{ cm} = 476 \text{ cm}^2

2. Area of the semicircle: The area of a full circle is A=πr2A = \pi r^2, where rr is the radius. Since the diameter is 28 cm, the radius rr is 1414 cm. The area of the semicircle is half of the full circle's area: Asemicircle=12×π×142 cm2A_{\text{semicircle}} = \frac{1}{2} \times \pi \times 14^2 \text{ cm}^2 Asemicircle=12×π×196 cm2=98π cm2307.88 cm2A_{\text{semicircle}} = \frac{1}{2} \times \pi \times 196 \text{ cm}^2 = 98\pi \text{ cm}^2 \approx 307.88 \text{ cm}^2

Total area AA is: A=476 cm2+98π cm2476 cm2+307.88 cm2783.88 cm2A = 476 \text{ cm}^2 + 98\pi \text{ cm}^2 \approx 476 \text{ cm}^2 + 307.88 \text{ cm}^2 \approx 783.88 \text{ cm}^2

Final Answers:

  • Perimeter: 105.96 cm\approx 105.96 \text{ cm}
  • Area: 783.88 cm2\approx 783.88 \text{ cm}^2

Do you want more details, or have any questions?

Related Questions:

  1. How would the perimeter change if the diameter of the semicircle were increased?
  2. What if the rectangle had a different height? How would that affect the area?
  3. How is the formula for the circumference of a circle derived?
  4. How would the calculations change if the shape was a quarter circle instead of a semicircle?
  5. Can the shape be split in another way to make the calculations simpler?

Tip: For composite shapes, always break them down into simpler components to calculate area and perimeter.

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter
Area
Circle
Semicircle

Formulas

Perimeter of composite shapes
Area of rectangle
Area of semicircle
Circumference of circle

Theorems

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Suitable Grade Level

Grades 7-9