Math Problem Statement

Find the perimeter and area of this shape.

Solution

Let's solve this problem by finding the perimeter and area of the composite shape.

1. Perimeter Calculation

The perimeter is the sum of the lengths of all outer edges. This shape consists of:

  • Two vertical sides of 6cm6 \, \text{cm} each.
  • Two horizontal sides of 9cm9 \, \text{cm} each.
  • A semicircular arc with radius 3cm3 \, \text{cm} (since the width of the rectangle is 6 cm, the diameter of the semicircle is also 6 cm, giving a radius of 3cm3 \, \text{cm}).

Semicircle Arc Length

The formula for the circumference of a circle is: C=2πrC = 2\pi r The arc length of the semicircle is half the circumference: Arc Length=πr=π×3=3πcm.\text{Arc Length} = \pi r = \pi \times 3 = 3\pi \, \text{cm}.

Total Perimeter

Adding all edges: Perimeter=6+6+9+9+3π.\text{Perimeter} = 6 + 6 + 9 + 9 + 3\pi. Substitute π3.14\pi \approx 3.14: Perimeter6+6+9+9+3(3.14)=30+9.42=39.42cm.\text{Perimeter} \approx 6 + 6 + 9 + 9 + 3(3.14) = 30 + 9.42 = 39.42 \, \text{cm}.

2. Area Calculation

The area of the shape can be computed as:

  • Area of the rectangle (9cm×6cm9 \, \text{cm} \times 6 \, \text{cm}).
  • Subtract the area of the semicircle (12πr2\frac{1}{2} \pi r^2).

Rectangle Area

Area of Rectangle=9×6=54cm2.\text{Area of Rectangle} = 9 \times 6 = 54 \, \text{cm}^2.

Semicircle Area

Area of Semicircle=12πr2=12π(3)2=12π×9=4.5π.\text{Area of Semicircle} = \frac{1}{2} \pi r^2 = \frac{1}{2} \pi (3)^2 = \frac{1}{2} \pi \times 9 = 4.5\pi. Substitute π3.14\pi \approx 3.14: Area of Semicircle4.5×3.14=14.13cm2.\text{Area of Semicircle} \approx 4.5 \times 3.14 = 14.13 \, \text{cm}^2.

Total Area

Area=Area of RectangleArea of Semicircle.\text{Area} = \text{Area of Rectangle} - \text{Area of Semicircle}. Area5414.13=39.87cm2.\text{Area} \approx 54 - 14.13 = 39.87 \, \text{cm}^2.


Final Answer:

  • Perimeter: 39.42cm\approx 39.42 \, \text{cm}
  • Area: 39.87cm2\approx 39.87 \, \text{cm}^2

Would you like further clarifications or more details?


Related Questions:

  1. How is the arc length of a circle calculated?
  2. How would the answer change if the semicircle were replaced with a full circle?
  3. What is the importance of π\pi in circle-related calculations?
  4. Can you explain how the formula for the circumference of a circle is derived?
  5. What happens to the area calculation if the semicircle is shifted to another side of the rectangle?

Tip:

When solving geometry problems with composite shapes, break the problem into smaller parts and handle one component at a time.

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter
Area
Composite Shapes
Circles

Formulas

Circumference of a circle: C = 2πr
Arc Length of a semicircle: Arc = πr
Area of a rectangle: A = length × width
Area of a semicircle: A = 1/2πr^2

Theorems

Perimeter and area calculations using composite geometry

Suitable Grade Level

Grades 7-9