Math Problem Statement

What is the perimeter and area of the shape made of part of a circle and a rectangle?

Solution

The problem involves determining both the perimeter and the area of a composite shape made of part of a circle and a rectangle. Let’s analyze and solve the problem step by step.


Observations:

  1. The shape includes:

    • A rectangle.
    • A semicircle attached to one side of the rectangle.
  2. The dimensions visible in the image:

    • The width of the rectangle (and the diameter of the semicircle) is 4 units.
    • The height of the rectangle is 3 units.
  3. The radius of the semicircle can be deduced:

    • Radius r=Diameter2=42=2unitsr = \frac{\text{Diameter}}{2} = \frac{4}{2} = 2 \, \text{units}.

(a) Perimeter of the Shape

The perimeter includes:

  1. The two vertical sides of the rectangle: 2×3=6units2 \times 3 = 6 \, \text{units}.
  2. The curved part of the semicircle (half the circumference of a full circle):
    Semicircle arc=12×2πr=πr=π×2=2πunits.\text{Semicircle arc} = \frac{1}{2} \times 2 \pi r = \pi r = \pi \times 2 = 2\pi \, \text{units}.

Thus, the total perimeter: P=6+2π6+6.28=12.28units.P = 6 + 2\pi \approx 6 + 6.28 = 12.28 \, \text{units}.


(b) Area of the Shape

The total area is the sum of:

  1. The area of the rectangle:
    Rectangle area=width×height=4×3=12square units.\text{Rectangle area} = \text{width} \times \text{height} = 4 \times 3 = 12 \, \text{square units}.

  2. The area of the semicircle:
    Semicircle area=12×πr2=12π(22)=12π(4)=2πsquare units.\text{Semicircle area} = \frac{1}{2} \times \pi r^2 = \frac{1}{2} \pi (2^2) = \frac{1}{2} \pi (4) = 2\pi \, \text{square units}.

Thus, the total area: A=12+2π12+6.28=18.28square units.A = 12 + 2\pi \approx 12 + 6.28 = 18.28 \, \text{square units}.


Final Answers:

(a) Perimeter: 12.28units\approx 12.28 \, \text{units}.
(b) Area: 18.28square units\approx 18.28 \, \text{square units}.

Would you like a step-by-step visual breakdown or further clarifications?


5 Related Questions:

  1. How does the formula for the circumference of a circle help in perimeter calculations for semicircles?
  2. What would happen to the perimeter and area if the semicircle were replaced by a full circle?
  3. How do we approximate π\pi when solving problems involving circles?
  4. How can composite shapes be divided to simplify area calculations?
  5. What is the difference between perimeter and circumference?

Tip:

Always ensure dimensions are in the same units before performing calculations in geometry.

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter
Area
Circles
Rectangles

Formulas

Perimeter of a rectangle: P = 2l + 2w
Circumference of a circle: C = 2πr
Area of a rectangle: A = l × w
Area of a circle: A = πr^2

Theorems

Perimeter of composite shapes
Area of composite shapes

Suitable Grade Level

Grades 6-8