Lines of symmetry – Grade 4 math lesson
Lesson 26 of 26 in the Grade 4 math course
US version. US grades, US spelling and dollars ($). · UK Maths Department
A complete 45-minute lesson for grade 4 (ages 9–10) that runs on this page – at school or at home. Every answer is graded right away, with a worked explanation.
- Time
- 45 minutes + 20 min homework
- Grade
- Grade 4 (ages 9–10)
- You need
- Paper, a pencil and this page
- Graded
- Instantly, with explanations
For parents: how to use this lesson
You don't need to know this topic yourself. The lesson explains each step on screen, one tidy step at a time. Every answer is graded straight away with a worked explanation, so you never have to grade anything.
- Read what your child will learn and the big ideas together.
- Press Start the lesson below and sit with your child for the teaching and the worked examples (about 19 minutes).
- Let them do the practice on their own. They choose Getting started, On track or Challenge – start on On track and move up after a few right in a row.
- Finish with the exit ticket and the talk question: “How many lines of symmetry does a circle have?”
- Later that day or the next day: the homework (20 minutes), then a practice test.
Watch out for
- Thinking a diagonal of a rectangle is a line of symmetry. Fold a paper rectangle along the diagonal: the halves do not match.
- Only looking for up-and-down lines. Check across and diagonally too.
Tip for home: Look for symmetry in leaves, butterflies, faces and letters.
What your child will learn
Learning goal: find lines of symmetry and complete symmetrical shapes.
Success looks like
- I can find lines of symmetry.
- I can complete a symmetrical shape.
- I can say how many lines of symmetry a shape has.
Key words
- symmetry
- when one half mirrors the other
- line of symmetry
- the fold line where halves match
- mirror line
- another name for a line of symmetry
- reflect
- flip over a line
What to have ready
- Paper and a pencil
- This page on a computer, tablet or phone
- For the hands-on part: Fold paper shapes to find lines of symmetry. Use a mirror on half a picture to see the whole.
The big ideas (for the adult)
A line of symmetry splits a shape into two halves that are mirror images.
If you fold a shape along a line of symmetry, the two halves match exactly.
Some shapes have several lines of symmetry; some have none. A regular shape has as many lines of symmetry as sides.
The lesson, step by step
| Part | Time | How it is checked |
|---|---|---|
| Starter: quick recall | 5 min | Graded by Classfern |
| Teaching input | 10 min | Not assessed, self-checked |
| Worked examples and guided practice | 9 min | Not assessed, graded by Classfern |
| Independent practice | 15 min | Graded by Classfern |
| Closure and exit ticket | 6 min | Graded by Classfern, self-checked |
Starter, "your turn", practice and exit ticket are graded by Classfern. Worked examples and teaching are not assessed. The hands-on task and the reflection are self-assessed. Explanations in talk are judged by the parent and not recorded.
The lesson
It runs here on the page. No sign-up and no names – progress is kept only in this browser.
Homework and practice at home
20 minutes: 10 practice questions, 3 multiple-choice questions and 2 to remember from earlier work, then a short reflection. New questions every time, all graded instantly.
More practice
More Grade 4 math lessons
- Factors and multiples
- Prime and composite numbers
- Multiplication and division
- Solving word problems
- Number patterns
- Place value: the value of each digit
- Rounding to the nearest 10, 100 or 1,000
- Adding with the standard algorithm
- Subtracting with the standard algorithm
- Decimals: tenths, hundredths and thousandths
- Comparing, ordering and writing numbers
- Equivalent fractions
- Adding and subtracting fractions with like denominators
- Fractions of a whole number
- Comparing and simplifying fractions
- Fractions, decimals and percentages
- Area of rectangles
- Perimeter
- Finding unknown angles
- Converting units of time
- Line plots
- Converting measurement units
- Measuring angles
- Classifying 2-D shapes
Curriculum
Common Core State Standards 4.G.A.3: “Recognize a line of symmetry for a two-dimensional figure as a line across the figure such that the figure can be folded along the line into matching parts. Identify line-symmetric figures and draw lines of symmetry.”
Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board.