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 these shapes (sides and corners).
• Find lines of symmetry in shapes.
• Draw lines of symmetry.
• Tell the difference between symmetrical and non-symmetrical shapes.

Lesson summary

This week, we're diving into the exciting world of 2D shapes and symmetry! Geometry is all around us, from the shapes of our homes and schools to the patterns in our clothing and the designs of our cultural art. Understanding 2D shapes and symmetry helps us appreciate the beauty and order in the world around us, and it also builds important problem-solving skills that you'll use in many other areas of Maths and in everyday life. Imagine trying to build a balanced structure without understanding symmetry, or describing the shape of a soccer field without knowing about rectangles! These skills are crucial for design, construction, art, and many other fields.

Lesson notes

2D Shapes: 2D shapes are flat shapes that only have two dimensions: length and width. They don't have thickness. Think of them as shapes you can draw on a piece of paper.

Square: A square has four sides that are all the same length and four corners (vertices) that are all right angles (like the corner of a page in a book).

Rectangle: A rectangle also has four sides and four right angles.

However, unlike a square, its opposite sides are equal in length, but not all four sides are equal.

Circle: A circle is a round shape with no corners or straight sides. All points on the circle are the same distance from the center.

Triangle: A triangle has three sides and three corners. There are different types of triangles, like equilateral triangles (all sides equal), isosceles triangles (two sides equal), and scalene triangles (no sides equal).

Pentagon: A pentagon has five sides and five corners.

Properties of 2D Shapes: Sides: The straight lines that form the shape.

Corners (Vertices): The points where the sides meet.

Angles: The space between two sides that meet at a corner. A right angle is a 90-degree angle, like the corner of a square or rectangle.

Example 1: Let's look at a rectangle. It has 4 sides and 4 corners (vertices). Its opposite sides are equal in length. All its angles are right angles.

Example 2: Now, let's consider a triangle. It has 3 sides and 3 corners (vertices). The angles inside a triangle can vary, and they always add up to 180 degrees.

Symmetry: Symmetry means that something is the same on both sides. A shape is symmetrical if you can draw a line down the middle of it and one half is a mirror image of the other half. This line is called the line of symmetry or the axis of symmetry. Imagine folding a picture along the line of symmetry - the two halves would match perfectly.

Example 3: A square has four lines of symmetry: one horizontal, one vertical, and two diagonal.

Example 4: A rectangle has two lines of symmetry: one horizontal and one vertical.

Example 5: A circle has an infinite number of lines of symmetry – you can draw a line through the center in any direction, and it will be symmetrical.

How to Find Lines of Symmetry: Visual Inspection: Look at the shape and imagine folding it in half. Does one half match the other?

Folding: If you have a physical copy of the shape, try folding it along different lines to see if the two halves match perfectly.

Drawing: Draw a line down the middle of the shape and see if the two halves look like mirror images. Symmetrical vs.

Non-Symmetrical Shapes: Symmetrical shapes have at least one line of symmetry. Non-symmetrical shapes do not have any lines of symmetry. These shapes look different on either side. For example, a scalene triangle (where all sides are different lengths) typically does not have any lines of symmetry. Guided Practice (With Solutions)

Question 1: Name the following shape and state how many sides and corners it has: [Image of a square].

Solution: This is a square. It has 4 sides and 4 corners (vertices). All sides are equal in length, and all angles are right angles.

Question 2: Draw a rectangle and show its lines of symmetry.

Solution: [Learners draw a rectangle].

A rectangle has two lines of symmetry: a vertical line down the middle and a horizontal line across the middle. [Teacher demonstrates drawing the lines of symmetry]. These lines divide the rectangle into two equal halves that are mirror images of each other.

Question 3: Is a circle symmetrical? If so, how many lines of symmetry does it have?

Solution: Yes, a circle is symmetrical. It has an infinite number of lines of symmetry because you can draw a line through the center in any direction and it will be symmetrical.

Question 4: Identify whether the following shape is symmetrical or non-symmetrical: [Image of an isosceles triangle]. If symmetrical, draw its line of symmetry.

Solution: This is an isosceles triangle (two sides are equal). It IS symmetrical. Its line of symmetry runs from the top vertex (corner) down to the midpoint of the opposite side (the base). [Teacher demonstrates drawing the line of symmetry]. Independent Practice (Questions Only) Name the following shape and state how many sides and corners it has: [Image of a triangle (not equilateral or isosceles)]. Draw a pentagon. Does a pentagon always have lines of symmetry? Explain your answer. Draw a square and show all its lines of symmetry. Is a shape that looks like the letter 'A' symmetrical? Draw the shape and show the line(s) of symmetry, if any. Is a shape that looks like the letter 'E' symmetrical? Draw the shape and show the line(s) of symmetry, if any. Draw a shape that has no lines of symmetry. Explain why it doesn't have any. [Image of a diamond shape - Rhombus, but tell them it's a kite]. This shape looks like a kite. How many lines of symmetry does it have? Look around the classroom. Name three objects that are 2D shapes. What shapes are they? Find three objects in your home that are symmetrical.