Angles, Symmetry and Data: Year 4 Study Guide
Year 4 students describe shapes more precisely and learn to read and make simple graphs.
An angle is the amount of turn between two lines that meet at a point. Students compare angles with a right angle (like the corner of a page) and call them acute (smaller than a right angle), right, obtuse (bigger than a right angle but less than a straight line) or reflex (bigger than a straight line). They estimate and measure angles in degrees with a protractor.
They describe symmetry (a shape that can be folded so the halves match) and transformations: flips (reflections), slides (translations) and turns (rotations). In Statistics they collect data, record it in tables and display it in graphs.
Types of angles
| Angle | Size | Where you see it |
|---|---|---|
| Acute | less than 90° | the tip of a pencil |
| Right | 90° | corner of a book |
| Obtuse | between 90° and 180° | a door opened wide |
| Straight | 180° | a flat line |
| Reflex | between 180° and 360° | the outside of a corner |
Symmetry and transformations
A square has four lines of symmetry, a rectangle has two and a regular hexagon has six. A flip creates a mirror image. A slide moves a shape without changing its direction. A turn rotates it around a point. After each transformation the shape is the same size and shape, only in a new position.
Fold the shape in half.
Do both halves match?
Draw the line of symmetry.
How many lines are there?
Data displays
Students collect data by a survey, put it in a table (tally marks and totals) and draw a picture graph or column graph. A key tells you what each symbol or square stands for. For example, if one symbol is 2 students, then 5 symbols mean 10 students. Questions to ask: which is most popular, which is least, and how many more?
| Favourite pet | Tally | Total |
|---|---|---|
| Dog | |||| |||| || | 12 |
| Cat | |||| ||| | 8 |
| Bird | |||| | 5 |
| Fish | ||| | 3 |
Worked examples and common mistakes
Example: Dogs have 12 votes and cats have 8, so dogs have 4 more votes. Common mistakes: thinking a longer arm makes a bigger angle, ignoring the key on a picture graph and miscounting tally groups of five. Re-count before you answer.
Check your understanding: model answers
1. Obtuse. 2. Two. 3. 12 votes.
✨ Key Takeaways
- Angles are compared with a right angle.
- Symmetry means both halves match.
- Flips, slides and turns move shapes.
- Check the key when reading a graph.
💬 Questions for Discussion & Reflection
- What kind of angle is 120°?
- How many lines of symmetry does a rectangle have?
- On a graph where each symbol is 2 votes, a bar has 6 symbols. How many votes?
Print graph paper for graphs →