Investigate different ways of decomposing a polygon | Maths

Starter quiz

Match the polygons to the correct name.
- a
  
  ⇔
  
  pentagon ✓
- b
  
  ⇔
  
  octagon ✓
- c
  
  ⇔
  
  quadrilateral ✓
- d
  
  ⇔
  
  triangle ✓
Match the parts of the sentence correctly.
- A polygon with 3 sides
  
  ⇔
  
  is a triangle. ✓
- A polygon with 5 sides
  
  ⇔
  
  is a pentagon. ✓
- A polygon with 6 sides
  
  ⇔
  
  is a hexagon. ✓
- A polygon with 8 sides
  
  ⇔
  
  is an octagon. ✓
Which of these are properties of a rectangle?
- 4 equal sides.
- Two pairs of parallel sides. ✓
- 4 right angles. ✓
Look at this pentagon. How many right angles does it have? ______ right angles
- '2' ✓
Look at this hexagon. How many right angles does it have? ______ right angles
- '0' ✓
This rectangle has been cut in half using a diagonal line. What shape will both halves be?
- squares
- rectangles
- triangles ✓

Exit quiz

How many pairs of parallel sides does this quadrilateral have?
- 0
- 1 ✓
- 2
- 3
The pentagon has been decomposed into three polygons. Match the name of the polygon to the correct letter.
- A
  
  ⇔
  
  triangle ✓
- B
  
  ⇔
  
  triangle ✓
- C
  
  ⇔
  
  quadrilatral ✓
This hexagon has been decomposed into two shapes. Select the names of the decomposed shapes.
- pentagon ✓
- triangle
- rectangle
- hexagon
- quadrilateral ✓
Two lines that meet at a right angle are called __________ lines.
- parallel
- perpendicular ✓
- curved
Look at the image. Which statements are true?
- This polygon is a quadrilateral
- It has one right angle ✓
- It has one pair of parallel sides
- It has one pair of perpendicular sides ✓
This octagon has been decomposed into 3 polygons. Match each polygon to the correct description.
- A
  
  ⇔
  
  has one pair of parallel sides. ✓
- B
  
  ⇔
  
  has only two right angles. ✓
- C
  
  ⇔
  
  has more than one pair of perpendicular sides. ✓

Worksheet

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Lesson Details

Key learning points

The same whole can be split into different parts.
Lines are perpendicular when they are at right angles to each other.
Lines are parallel because they are always the same distance apart.

Common misconception

Pupils are not able to identify right angles and therefore struggle to identify pairs of perpendicular sides.

Provide children with a right angle checker. Take time to model its use, focusing on aligning one edge of the checker with a side of the angle they want to check.

Keywords

Polygon - A polygon is a 2D shape made up of three or more straight lines.
Quadrilateral - A quadrilateral is a polygon that has four straight sides and four vertices.
Parallel - Parallel lines are straight lines that are always the same distance apart. They never get closer together or further apart.
Decompose - To decompose means to break something into parts that are the same as the original when you put them back together.