Lesson 2: Area of Plane Shapes and Circles

👨🏽‍🏫 Introduction

Imagine you’re helping to lay tiles on a rectangular floor, paint a circular signboard, or fence a triangular garden. To do these things efficiently, you need to know how much space each shape covers — in other words, their area.

In this lesson, we’ll review and apply formulas to calculate the area of different 2D plane shapes, including rectangles, triangles, parallelograms, trapeziums, and circles. These skills are vital in carpentry, farming, construction, and even sewing!

• 🧱 Find the area of rectangles, squares, and triangles
• 🔷 Work with trapeziums and parallelograms
• 🟠 Calculate the area of circles using

🧠 Key Concepts and Area Formulas

📐 Area Formulas You Must Know

• Rectangle:
• Square:
• Triangle:
• Parallelogram:
• Trapezium:
• Circle:

🔁 Units of Area

Always express area in square units, such as:

• cm² – square centimetres
• m² – square metres
• km² – square kilometres (used for large land areas)

🔍 Worked Examples

1. 1. Area of a rectangle: A classroom floor is 8 m long and 5 m wide. What is its area?
      
      🟢 The floor covers 40 square metres.

1. 1. Area of a triangle: A triangular sign has a base of 6 cm and a height of 4 cm.
      
      🟢 The area of the sign is 12 square centimetres.

1. 1. Area of a trapezium: A field has two parallel sides of lengths 10 m and 16 m, and the height is 6 m.
      
      🟢 The field covers 78 m².

1. Area of a circle: A circular mat has a radius of 7 cm. Use .
   
   🟢 The mat covers approximately 153.86 cm².

✍🏽 Practice Exercises

🅰️ Section A – Basic Shapes

1. A square has a side length of 9 cm. Find its area.
2. A rectangle has length 12 m and width 4 m. What is its area?

🅱️ Section B – Triangles and Parallelograms

1. Find the area of a triangle with base 10 cm and height 5 cm.
2. A parallelogram has a base of 8 cm and a height of 3 cm. Find its area.

🅾️ Section C – Trapeziums and Circles

1. A trapezium has bases 6 m and 14 m, and a height of 5 m. Find its area.
2. A circular pond has a radius of 10 m. Use to find its area.

✅ Answers and Explanations

• A1:
• A2:
• B1:
• B2:
• C1:
• C2:

📌 Recap

• ✅ Each 2D shape has a specific formula for area
• ✅ Always check the units and make sure measurements match
• ✅ Remember: area is always in square units (e.g., cm², m²)

💭 Reflection Prompt

Pick any object around you — your phone screen, a tabletop, a circular bowl. Estimate its dimensions and try calculating its area using the correct formula. What did you discover?