MathIsimple
Back to Unit 4

Lesson 4-3: Area & Perimeter Applications

Scenario: Landscaping Design - Learn to calculate areas and perimeters through garden and room design projects!

Duration: 65-80 minutesScenario: Landscaping Design

Learning Objectives

  • Calculate areas of rectangles, triangles, and circles
  • Find perimeters of various shapes
  • Work with complex composite shapes
  • Apply formulas to real-world design problems

Landscaping Design Scenario

The Problem

You're designing a backyard garden with multiple sections. You need to calculate the area for planting and the perimeter for fencing. The garden includes a rectangular lawn, a triangular flower bed, and a circular pond.

Design Challenge:
Calculate the total area and perimeter for a garden with:
• Rectangular lawn: 12 ft × 8 ft
• Triangular flower bed: base 6 ft, height 4 ft
• Circular pond: radius 3 ft

Garden Layout

Lawn
12×8 ft
Flower
6×4 ft
Pond
r=3 ft

Composite garden design with multiple shapes

Area Formulas

Basic Shapes

Rectangle

A = length × width

Example: 12 × 8 = 96 ft²

Triangle

A = ½ × base × height

Example: ½ × 6 × 4 = 12 ft²

Circle

A = π × r²

Example: π × 3² ≈ 28.3 ft²

Perimeter Formulas

Basic Shapes

Rectangle

P = 2(length + width)

Example: 2(12 + 8) = 40 ft

Triangle

P = side₁ + side₂ + side₃

Example: 6 + 5 + 5 = 16 ft

Circle

C = 2π × r

Example: 2π × 3 ≈ 18.8 ft

Solving the Garden Problem

Calculating Areas

Rectangular Lawn: A = 12 × 8 = 96 ft²

Triangular Flower Bed: A = ½ × 6 × 4 = 12 ft²

Circular Pond: A = π × 3² = 9π ≈ 28.3 ft²

Total Area: 96 + 12 + 28.3 = 136.3 ft²

Calculating Perimeters

Rectangular Lawn: P = 2(12 + 8) = 40 ft

Triangular Flower Bed: P = 6 + 5 + 5 = 16 ft (assuming isosceles)

Circular Pond: C = 2π × 3 = 6π ≈ 18.8 ft

Composite Shapes

Room Design Example

A room has an L-shaped layout. The main area is 10 ft × 12 ft, and there's a 4 ft × 6 ft extension. Find the total area and perimeter for flooring and baseboard installation.

Main Area: 10 × 12 = 120 ft²

Extension: 4 × 6 = 24 ft²

Total Area: 120 + 24 = 144 ft²

Perimeter: Calculate outer boundary = 2(16) + 2(12) = 56 ft

Practice Problems

Problem 1: Simple Area

A rectangular patio is 15 ft long and 10 ft wide. Find the area and perimeter.

Your solution:

Problem 2: Composite Shape

A garden has a 8m × 6m rectangular lawn with a 3m radius circular flower bed. Find the total area.

Your calculation: