Lesson 3.2: Measurement – Perimeter Word Problems, Compound Shapes & Area | SEA Mathematics | My Carib Academy
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📏 Lesson 3.2: Measurement – Perimeter Word Problems, Compound Shapes & Area

Master perimeter word problems, compound shapes, and area on grids & formulae for squares/rectangles. This lesson covers SEA Mathematics Objectives 143-151 from the Measurement Strand.

65 Minutes
Module 3: Measurement
Objectives 143-151
3 Videos
Lesson Progress 0%

Previous Lesson

Did you complete Lesson 3.1? Review Angles & Turns →

Learning Objectives

By the end of this lesson, you will be able to:

  • Solve perimeter word problems involving squares and rectangles (Objectives 143-144)
  • Calculate perimeter of compound shapes (Objectives 143-144)
  • Find area by counting squares on a grid (Objectives 145-148)
  • Use formulae to calculate area of squares and rectangles (Objectives 149-151)
  • Solve word problems involving area

SEA Tip

Perimeter and area questions appear in Section I, II, and III of the SEA Math paper. Know your formulas! (SEA Framework Page 25-26)

Watch: Perimeter Word Problems

Start by watching this video to learn how to solve perimeter word problems. Take notes as you watch! 📝

Perimeter Word Problems – Mathematics Video Lesson

Quick Check

Did you understand the video? Review the notes below before continuing! ✅

Perimeter Word Problems

Perimeter word problems involve finding the distance around a shape in real-life situations!

Perimeter Formulas

  • Square: Perimeter = 4 × side (P = 4s)
  • Rectangle: Perimeter = 2 × (length + width) (P = 2(l + w))
  • Any Shape: Add all the sides together

📊 Example 1: Perimeter Word Problem

Fencing a Garden

Question: A rectangular garden is 12 m long and 8 m wide. How much fencing is needed to go around it?

Solution:

  1. Identify: Length = 12 m, Width = 8 m
  2. Formula: P = 2 × (length + width)
  3. Substitute: P = 2 × (12 + 8)
  4. Calculate: P = 2 × 20 = 40 m

Answer: 40 m of fencing needed

📊 Example 2: Perimeter Word Problem

Running Around a Field

Question: A square field has sides of 50 m. If John runs around it 3 times, how far does he run?

Solution:

  1. Find perimeter: P = 4 × 50 = 200 m
  2. Multiply by laps: 200 × 3 = 600 m

Answer: 600 m

Watch: Perimeter of Compound Shapes

Now watch this video to learn how to find the perimeter of compound shapes. Pay attention! 🎯

Perimeter of Compound Shapes – Mathematics Video Lesson

Perimeter of Compound Shapes

Compound shapes are made by combining two or more simple shapes. To find the perimeter, add all the outside sides!

📋 How to Find Perimeter of Compound Shapes:

Step-by-Step Method
  1. Identify all the outside sides (don’t count inside lines!)
  2. Find any missing side lengths using the given information
  3. Add all the outside sides together
  4. Include the units (cm, m, etc.)

📊 Example 3: L-Shaped Compound Shape

6 cm 2 cm 4 cm 6 cm 2 cm 4 cm

L-Shape

Perimeter = 6+2+4+4+2+6 = 24 cm

📊 Example 4: Finding Missing Sides

Compound Shape with Missing Side

Question: Find the perimeter of this compound shape. (Total length = 10 cm, One side = 6 cm, Find missing side)

Solution:

  1. Find missing side: 10 − 6 = 4 cm
  2. Add all outside sides: 10 + 5 + 6 + 3 + 4 + 2 = 30 cm

Answer: 30 cm

Common Mistake

Don’t count the inside lines! Only add the outside edges when finding perimeter of compound shapes.

Watch: Area on Grids & Formulae

Watch this video to learn how to find area using grids and formulae for squares and rectangles. 🎯

Area on Grids & Formulae for Squares/Rectangles – Mathematics Video Lesson

Area on Grids

Area is the amount of space inside a shape. We measure area in square units (cm², m², etc.).

📋 Finding Area by Counting Squares:

4 squares 3 squares Area = 12 squares

Count each square inside the shape

Counting Squares Method
  1. Count all the full squares inside the shape
  2. Combine half squares to make full squares (2 halves = 1 full)
  3. Add them all together
  4. Write the answer with square units (cm², m²)

Area Formulae for Squares & Rectangles

Instead of counting squares, we can use formulas to find area quickly!

Area Formulas

  • Square: Area = side × side (A = s²)
  • Rectangle: Area = length × width (A = l × w)

📊 Example 5: Area of a Square

5 cm 5 cm A = 25 cm²

Square

Side = 5 cm
A = 5 × 5 = 25 cm²

📊 Example 6: Area of a Rectangle

8 cm 5 cm A = 40 cm²

Rectangle

L = 8 cm, W = 5 cm
A = 8 × 5 = 40 cm²

📊 Example 7: Area Word Problem

Tiling a Floor

Question: A room is 6 m long and 4 m wide. How many square meters of tiles are needed?

Solution:

  1. Identify: Length = 6 m, Width = 4 m
  2. Formula: Area = length × width
  3. Calculate: A = 6 × 4 = 24 m²

Answer: 24 m² of tiles needed

Memory Trick

Perimeter = Distance AROUND (fence around a yard)
Area = Space INSIDE (grass inside the fence)
Perimeter = units (m, cm), Area = square units (m², cm²)

Quick Quiz

Test your understanding! Select an answer for each question. 📏

6 Questions
12 Minutes
70% to Pass

1. A rectangle is 10 m long and 6 m wide. What is the perimeter?

2. A square has sides of 7 cm. What is the area?

3. What is the perimeter of a square with side 9 m?

4. A rectangle has length 12 cm and width 5 cm. What is the area?

5. What do we measure area in?

6. A garden is 15 m long and 10 m wide. How much fencing is needed?

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Lesson Complete!

Great job finishing Lesson 3.2! You’re mastering perimeter and area for the SEA exam! 🎉

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