Math Problem Statement

Find the perimeter of the figure. (Use π = 3).

Solution

To solve the problem and find the perimeter of the given figure, let's break it down step by step:

Step 1: Analyze the figure

The figure consists of:

  1. A straight horizontal segment of 9 cm.
  2. Two vertical sides of 2 cm each.
  3. A semi-circular curve at the bottom with a radius of 2 cm.
  4. A triangular cutout with a base of 4 cm and a vertical height of 2 cm.
  5. A horizontal segment of 3 cm within the triangular cutout.

Step 2: Calculate the curved length (semi-circle perimeter)

The semi-circle's perimeter is half the circumference of a full circle. Using the formula C=πdC = \pi \cdot d, and given the radius r=2r = 2 cm (so d=4d = 4 cm) and π=3\pi = 3, Semi-circle length=12πd=1234=6cm.\text{Semi-circle length} = \frac{1}{2} \cdot \pi \cdot d = \frac{1}{2} \cdot 3 \cdot 4 = 6 \, \text{cm}.

Step 3: Add all the line segments

The total length of the perimeter is: 9cm (top horizontal)+2cm (right vertical)+6cm (semi-circle)+2cm (left vertical).9 \, \text{cm (top horizontal)} + 2 \, \text{cm (right vertical)} + 6 \, \text{cm (semi-circle)} + 2 \, \text{cm (left vertical)}.

Since the triangle's 4 cm base is not part of the perimeter due to the cutout, it is excluded.

Perimeter=9+2+6+2=19cm.\text{Perimeter} = 9 + 2 + 6 + 2 = 19 \, \text{cm}.

Final Answer:

The perimeter of the figure is 19 cm.

Do you need further clarification, or have any questions about this calculation?

Follow-Up Questions:

  1. Why does the triangle’s base not contribute to the perimeter?
  2. How would the calculation change if the radius of the semi-circle were doubled?
  3. Can we generalize this formula for figures with multiple semi-circles?
  4. Why is π=3\pi = 3 used instead of the more precise value 3.143.14?
  5. How does the triangular cutout affect the calculation?

Tip:

When dealing with composite shapes, break them into smaller, manageable parts and calculate each component separately!

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter calculation
Properties of semi-circles
Composite figures

Formulas

Circumference of a circle: C = π × d
Semi-circle perimeter: (1/2) × π × d

Theorems

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Suitable Grade Level

Grades 6-8