Line of Symmetry – Basic 3 Mathematics Lesson Note (Third Term)

A. counting skill: numbers 961-980

Counting from 961 to 980: 961, 962, 963, 964, 965, 966, 967, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980

Practice counting:

• From 965 to 975: _______
• From 972 to 980: _______
• Backwards from 980 to 970: _______

Fill in missing numbers:

• 966, 967, _____, 969, _____
• 975, _____, 977, _____, 979
• _____, 962, _____, 964, _____

B. writing skill: writing of the numbers

Write in words:

• 961 = Nine hundred and sixty-one
• 965 = Nine hundred and sixty-five
• 970 = Nine hundred and seventy
• 975 = Nine hundred and seventy-five
• 980 = Nine hundred and eighty

Write in figures:

• Nine hundred and sixty-three = _______
• Nine hundred and sixty-eight = _______
• Nine hundred and seventy-two = _______
• Nine hundred and seventy-seven = _______
• Nine hundred and seventy-nine = _______

C. line(s) of symmetry

What is symmetry? 

A shape has symmetry when one half looks exactly like the other half when folded.

What is a line of symmetry? A line of symmetry is the imaginary line that divides a shape into two equal halves.

How to find a line of symmetry:

1. Imagine folding the shape
2. If both halves match exactly, there is a line of symmetry
3. The fold line is the line of symmetry

Examples of symmetrical objects:

• Butterfly (1 line of symmetry)
• Human face (1 line of symmetry)
• Letter A (1 line of symmetry)
• Letter H (2 lines of symmetry)

Examples of shapes with symmetry:

Square:        Rectangle:     Circle:

+—+          +—–+        —

|   |          |     |       /   \

| | |          |  |  |      |  |  |

|   |          |     |       \   /

+—+          +—–+        —

4 lines        2 lines       Many lines

Practice identifying symmetry: Draw the line(s) of symmetry for these letters:

1. Letter B: _____ line(s)
2. Letter O: _____ line(s)
3. Letter X: _____ line(s)
4. Letter M: _____ line(s)

D. properties of square, rectangle and triangle

SQUARE PROPERTIES:

• 4 equal sides
• 4 right angles (90°)
• 4 lines of symmetry
• All sides are the same length

Lines of symmetry in a square:

• 2 diagonal lines
• 1 vertical line through middle
• 1 horizontal line through middle

RECTANGLE PROPERTIES:

• 4 sides (opposite sides equal)
• 4 right angles (90°)
• 2 lines of symmetry
• Length is longer than width

Lines of symmetry in a rectangle:

• 1 vertical line through middle
• 1 horizontal line through middle

TRIANGLE PROPERTIES:

• 3 sides
• 3 angles
• Number of lines of symmetry depends on triangle type

Types of triangles and their symmetry:

• Equilateral triangle (all sides equal): 3 lines of symmetry
• Isosceles triangle (2 sides equal): 1 line of symmetry
• Scalene triangle (no equal sides): 0 lines of symmetry

Practice:

1. How many lines of symmetry does a square have? _____
2. How many lines of symmetry does a rectangle have? _____
3. How many sides does a triangle have? _____
4. How many right angles does a square have? _____

E. curves and straight lines

What is a straight line? A straight line goes in one direction without bending.

What is a curve? A curve is a line that bends or turns.

Examples of straight lines:

• Edge of a ruler
• Side of a book
• Edge of a table

Examples of curves:

• Circle
• Letter S
• Arc (part of a circle)
• Letter C

Shapes made with straight lines:

• Square (4 straight lines)
• Rectangle (4 straight lines)
• Triangle (3 straight lines)

Shapes made with curves:

• Circle (1 curved line)
• Oval (1 curved line)

Mixed shapes (straight lines and curves):

• Letter D (1 straight line + 1 curve)
• Letter P (2 straight lines + 1 curve)

Practice identifying:

1. Circle the shapes made only with straight lines: Square, Circle, Triangle, Rectangle, Oval
2. Circle the shapes made only with curves: Square, Circle, Triangle, Rectangle, Oval
3. How many straight lines make a triangle? _____
4. How many curved lines make a circle? _____

Drawing practice:

1. Draw a shape with 3 straight lines: _______
2. Draw a shape with 1 curved line: _______
3. Draw a letter made with straight lines only: _______
4. Draw a letter made with curves only: _______

F. quantitative reasoning

Symmetry word problems:

1. Kemi draws a square. How many lines of symmetry does her square have?
2. Tolu folds a rectangle along its line of symmetry. How many equal parts does he get?
3. A butterfly has 1 line of symmetry. If one wing has 5 spots, how many spots should the other wing have?

Shape analysis:

1. Which shape has more lines of symmetry: a square or a rectangle?
2. Name a shape that has no lines of symmetry: _______
3. Name a shape that has many lines of symmetry: _______

Line identification: Count the lines:

1. How many straight lines in the letter H? _____
2. How many curved lines in the letter O? _____
3. How many lines of symmetry in the letter I? _____

Real-life symmetry: Find symmetry in these objects:

1. Car (from front view): _____ line(s) of symmetry
2. Airplane (from above): _____ line(s) of symmetry
3. Flower with 6 equal petals: _____ line(s) of symmetry

CLASS EXERCISES

1. Count from 968 to 978:
2. Write in words:
   1. 967 = _______
   2. 973 = _______
   3. 980 = _______
3. Lines of symmetry:
   1. Square: _____ lines
   2. Rectangle: _____ lines
   3. Circle: _____ lines
   4. Equilateral triangle: _____ lines
4. Shape properties:
   1. How many sides does a square have? _____
   2. How many right angles does a rectangle have? _____
   3. How many sides does a triangle have? _____
5. Straight lines or curves:
   1. Triangle is made of _____ lines
   2. Circle is made of _____ line(s)
   3. Rectangle is made of _____ lines
   4. Letter O is made of _____ line(s)
6. Draw lines of symmetry:
   1. Draw 1 line of symmetry on letter A
   2. Draw 2 lines of symmetry on letter H
   3. Draw 4 lines of symmetry on a square
7. Identify symmetrical letters: Circle the letters that have lines of symmetry: A, B, C, D, H, M, O, X
8. Word problems:
   1. A square paper is folded along all its lines of symmetry. How many small squares are formed?
   2. If a shape has 2 lines of symmetry and 4 equal sides, what shape is it?
9. Complete the symmetrical pattern: If one half shows: ●○●, the other half should show: _______
10. Problem solving: Ada cuts out a heart shape. She says it has 1 line of symmetry. Is she correct? Draw the heart and show the line of symmetry if it exists.