Lesson Notes By Weeks and Term v5 - Grade 4

Lesson Video

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Performance objectives

• Identify and name common 2D shapes
• Describe the properties of 2D shapes
• Identify lines of symmetry in 2D shapes
• Draw lines of symmetry on 2D shapes
• Sort shapes based on symmetry

Lesson summary

Welcome, Grade 4 learners! This week, we are going on a geometric adventure to explore the fascinating world of 2D shapes and symmetry. Geometry isn't just about shapes on paper; it's all around us! From the rectangular shape of our school buildings to the circular wheels of a taxi, and even the beautiful symmetrical patterns in Ndebele art, understanding shapes helps us make sense of our world. Learning about symmetry helps us appreciate the beauty and balance that exists in nature and in the things people create. Think about the symmetrical patterns you see on a butterfly's wings or in the tiles of your home.

Lesson notes

2D Shapes: 2D shapes are flat shapes that only have two dimensions: length and width. They don't have thickness. Imagine drawing a shape on a piece of paper – that's a 2D shape!

Let's explore some common 2D shapes: Circle: A round shape with no corners or straight sides.

Examples in South Africa: the sun, a wheel, the face of a clock.

Square: A shape with four straight sides that are all equal in length, and four corners that are all right angles (like the corner of a textbook).

Examples in South Africa: some paving stones, some windows.

Rectangle: A shape with four straight sides and four right angles. Opposite sides are equal in length.

Examples in South Africa: a door, a chalkboard, a book.

Triangle: A shape with three straight sides and three corners.

There are different types of triangles: Equilateral triangle: All three sides are equal.

Isosceles triangle: Two sides are equal.

Scalene triangle: No sides are equal.

Right-angled triangle: One angle is a right angle (90 degrees).

Examples in South Africa: the shape of a warning sign, the gable of some houses.

Pentagon: A shape with five straight sides and five corners.

Example: Not very common, but some building designs might incorporate pentagons.

Hexagon: A shape with six straight sides and six corners.

Examples in South Africa: Honeycomb cells, some nuts and bolts.

Properties of 2D Shapes: Each shape has unique properties that help us identify it.

These properties include: Number of Sides: How many straight lines make up the shape?

Number of Corners/Vertices: How many points are where the sides meet? (Corners and vertices are the same thing!) Let’s look at some examples: Square: 4 sides, 4 corners/vertices Triangle: 3 sides, 3 corners/vertices Pentagon: 5 sides, 5 corners/vertices Symmetry: Symmetry is when a shape can be folded in half so that both halves match perfectly. The line where you fold the shape is called the line of symmetry (also known as the axis of symmetry). It's like looking at a mirror image! Not all shapes have symmetry, and some shapes have more than one line of symmetry. To test for symmetry, you can: Fold the shape: If the two halves match exactly, it's symmetrical.

Draw a line: Imagine a line going through the middle of the shape. If the shape looks the same on both sides of the line, it's symmetrical.

Examples of Lines of Symmetry: Square: Has 4 lines of symmetry (one vertical, one horizontal, and two diagonal).

Rectangle: Has 2 lines of symmetry (one vertical and one horizontal).

Circle: Has infinite lines of symmetry (any line that goes through the center).

Equilateral Triangle: Has 3 lines of symmetry (each going from a corner to the middle of the opposite side).

Isosceles Triangle: Has 1 line of symmetry (from the top corner to the middle of the base).

Scalene Triangle: Has 0 lines of symmetry. Guided Practice (With Solutions)

Question 1: What shape has 3 sides and 3 corners?

Solution: This is a triangle. A triangle is defined as a shape with three straight sides and three vertices (corners).

Question 2: Draw a square and draw all its lines of symmetry. How many lines of symmetry does it have?

Solution: [Imagine a square drawn here with dotted lines showing the vertical, horizontal, and two diagonal lines of symmetry] A square has 4 lines of symmetry. The vertical and horizontal lines split the square into two equal rectangles, while the diagonal lines split it into two equal right-angled triangles.

Question 3: Does a rectangle always have the same number of lines of symmetry as a square? Explain your answer.

Solution: No, a rectangle does not always have the same number of lines of symmetry as a square. A rectangle has two lines of symmetry (vertical and horizontal), while a square has four (vertical, horizontal, and two diagonal). This is because all sides of a square are equal, allowing for diagonal symmetry, which a rectangle doesn’t have because its sides are not all equal.

Question 4: Look at the letter "A". Does it have a line of symmetry? If so, draw it.

Solution: [Imagine the letter A drawn here with a vertical dotted line down the middle] Yes, the letter "A" (in its capital form) has one line of symmetry. The line runs vertically down the middle of the letter. Independent Practice (Questions Only) Name three 2D shapes you can find in your classroom. How many sides and corners does a hexagon have? Draw a circle. How many lines of symmetry does a circle have? Draw a rectangle. Draw its lines of symmetry. How many does it have? Which type of triangle has no lines of symmetry? Which of these shapes has more than 2 lines of symmetry: square, rectangle, triangle? Draw a pentagon. Does it have any lines of symmetry? (This may require research on regular pentagons).

Sort these shapes into two groups: shapes with lines of symmetry and shapes without lines of symmetry: triangle, circle, square, scalene triangle, rectangle, isosceles triangle. A window is shaped like a rectangle. It is 1 meter wide and 2 meters tall.