Lesson Notes By Weeks and Term v5 - Grade 3

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Calculate the perimeter of simple shapes.
• Find the area of shapes by counting squares.
• Explain the difference between perimeter and area.
• Define volume and identify objects with volume.
• Understand that volume is measured using cubes.

Lesson summary

This week, we are diving into the exciting world of measurement! Understanding measurement is super important because it helps us in our everyday lives. Imagine you are helping your mom bake koeksisters for a family gathering. You need to measure the ingredients correctly! Or maybe you are building a sandcastle at Durban beach and want to know how big it is. That's where perimeter, area, and volume come in handy. We'll start by learning about perimeter, then move on to finding the area of shapes by counting squares, and finally, get a sneak peek into what volume is all about. This will help us become amazing problem solvers and be able to understand the world around us better.

Lesson notes

Perimeter: Perimeter is the distance around the outside of a shape. Think of it like building a fence around your garden. You need to know the perimeter to know how much fencing you need! To find the perimeter, you simply add up the lengths of all the sides of the shape.

Example 1: Imagine a rectangular garden. One side is 5 meters long, and the other side is 3 meters long. Remember, in a rectangle, opposite sides are equal.

Side 1: 5 meters Side 2: 3 meters Side 3: 5 meters Side 4: 3 meters Perimeter = 5 + 3 + 5 + 3 = 16 meters So, you would need 16 meters of fencing to go around your garden.

Example 2: A square has all four sides equal. Let’s say each side of a square is 4 centimeters.

Side 1: 4 cm Side 2: 4 cm Side 3: 4 cm Side 4: 4 cm Perimeter = 4 + 4 + 4 + 4 = 16 cm Example 3: A triangle has three sides. Let’s say a triangle has sides that are 6cm, 8cm and 10cm. Perimeter = 6 + 8 + 10 = 24cm Area (Counting Squares): Area is the amount of space inside a shape. Imagine covering a floor with tiles; the area tells you how many tiles you need. We'll start by finding area by counting squares on a grid. Each square on the grid represents a unit of area (e.g., 1 square centimeter).

Example 1: Imagine a rectangle drawn on grid paper. It covers 5 squares across and 3 squares down. To find the area, we count the squares: 5 x 3 = 15 squares. We can say the area is 15 square units. If each square was a centimeter, it would be 15 square centimeters.

Example 2: Imagine an irregular shape (like a puddle) drawn on grid paper. Some squares are fully inside the shape, and some are only partly inside. Count the full squares inside the shape. For the squares that are about half full, count them as half squares. Add the number of full squares and half squares to estimate the area. Let’s say there are 10 full squares and 6 half squares. The area is approximately 10 + (6 / 2) = 10 + 3 = 13 square units.

Example 3: A shape covering exactly 4 whole squares and 2 half squares. The area would be 4 + (2/2) = 4+1 = 5 square units. Perimeter vs.

Area: Perimeter is the distance around a shape (like a fence), and area is the amount of space inside a shape (like the grass in the garden). Think about your classroom. The perimeter is the length of the walls, and the area is the size of the floor.

Volume (Introduction): Volume is the amount of space a 3D object takes up. Think of filling a container with water or sand. The volume tells you how much water or sand it can hold. We will start with a conceptual understanding of volume and understand that it is measured using cubes.

Example 1: A shoe box takes up more space than a small eraser.

Therefore, the shoe box has a greater volume.

Example 2: A water bottle can hold a certain amount of water. The amount of water it can hold is the volume of the bottle. Imagine building something with small blocks. The more blocks you use, the larger the volume of your construction. We measure volume using cubes (imagine sugar cubes fitting inside a box). Next year, you’ll learn more about measuring volume with units like cubic centimeters. Guided Practice (With Solutions)

Question 1: A rectangular picture frame has sides of 20cm and 15cm. What is the perimeter of the frame?

Solution: Side 1: 20 cm Side 2: 15 cm Side 3: 20 cm Side 4: 15 cm Perimeter = 20 + 15 + 20 + 15 = 70 cm

Commentary: We added the lengths of all four sides to find the total distance around the frame.

Question 2: A shape on grid paper covers 8 full squares and 4 half squares. What is the approximate area of the shape?

Solution: Full squares: 8 Half squares: 4 Area = 8 + (4 / 2) = 8 + 2 = 10 square units

Commentary: We counted the full squares and added half of the number of half squares to get an estimate of the total area.

Question 3: A triangular sign has sides that measure 30cm, 40cm, and 50cm. What is the perimeter of the sign?

Solution: Side 1 = 30cm Side 2 = 40cm Side 3 = 50cm Perimeter = 30 + 40 + 50 = 120cm

Commentary: We need to add up the length of all the sides of the triangle to get the perimeter.

Question 4: You have a square garden with each side measuring 6 meters. You want to build a fence around it. How many meters of fencing do you need?

Solution: Each side = 6m Perimeter = 6 + 6 + 6 + 6 = 24 meters

Commentary: Since a square has four equal sides, we add the length of the side four times to calculate the perimeter.

Question 5: Which has more volume: a tennis ball or a soccer ball? Briefly explain why.

Solution: A soccer ball has more volume than a tennis ball. This is because the soccer ball is bigger and takes up more space.

Commentary: This assesses a beginning understanding of volume and uses everyday objects to compare. Independent Practice (Questions Only) A rectangular table is 1 meter long and 0.5 meters wide. What is the perimeter of the table? A shape on grid paper covers 12 full squares and 8 half squares. What is the approximate area of the shape?