Calculating Area of Composite Shapes

Nov 24, 2024

Finding the Area of Composite Shapes

Introduction

  • Topic: Finding areas of complex shapes by decomposing them into simpler shapes.
  • Challenge: Strange shapes don't have predefined area formulas like rectangles or triangles.
  • Solution: Break complex shapes into simple shapes with known formulas.

Simple Shapes and Their Formulas

  • Rectangles: Area = Length x Width
  • Parallelograms: Formula not specified in transcript
  • Triangles: Area = 1/2 x Base x Height
  • Trapeziums: Area = (a + b)/2 x Height

Approach to Composite Shapes

  • Composite Shapes: Made of two or more simple shapes.
  • Strategy: Split the shape into rectangles, triangles, and/or trapeziums and calculate each area separately.

Example 1: Composite Shape Breakdown

  • Shape Description: Top part is a triangle, bottom part is a rectangle.
  • Steps:
    1. Rectangle Area:
      • Formula Used: Length x Width
      • Calculation: 5cm x 4cm = 20cm²
    2. Triangle Area:
      • Formula Used: 1/2 x Base x Height
      • Given: Base = 5cm, Height needs calculation
      • Height Calculation: Overall height = 7cm, Rectangle height = 4cm
      • Height of Triangle: 7cm - 4cm = 3cm
      • Area Calculation: 1/2 x 5cm x 3cm = 7.5cm²
    3. Total Area: 20cm² + 7.5cm² = 27.5cm²

Example 2: Composite Shape with Trapezium

  • Shape Description: Bottom is a rectangle, top is a trapezium.
  • Steps:
    1. Rectangle Area:
      • Formula Used: Length x Width
      • Calculation: 15cm x 12cm = 180cm²
    2. Trapezium Area:
      • Formula Used: (a + b)/2 x Height
      • Given: Top length (a) = 4cm, Bottom length (b) = 6cm, Height = 5cm
      • Average Length Calculation: (4cm + 6cm)/2 = 5cm
      • Area Calculation: 5cm x 5cm = 25cm²
    3. Total Area: 180cm² + 25cm² = 205cm²

Conclusion

  • Composite shapes can be broken down into simple shapes with known area formulas.
  • Calculation involves finding and summing the areas of each simple shape.

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