New
New
Year 3

Investigate different ways of decomposing a polygon

I can decompose a polygon in different ways and identify properties of polygons.

New
New
Year 3

Investigate different ways of decomposing a polygon

I can decompose a polygon in different ways and identify properties of polygons.

warning

These resources will be removed by end of Summer Term 2025.

Switch to our new teaching resources now - designed by teachers and leading subject experts, and tested in classrooms.

Lesson details

Key learning points

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

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.

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.

Decomposing shapes is a really useful tool for later thinking about area, fractions and spatial reasoning. Ensure pupils have adequate time in this lesson to decompose polygons and discuss similarities and differences.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

Loading...

6 Questions

Q1.
Match the polygons to the correct name.
An image in a quiz
Correct Answer:a,pentagon

pentagon

Correct Answer:b,octagon

octagon

Correct Answer:c,quadrilateral

quadrilateral

Correct Answer:d,triangle

triangle

Q2.
Match the parts of the sentence correctly.
Correct Answer:A polygon with 3 sides,is a triangle.

is a triangle.

Correct Answer:A polygon with 5 sides,is a pentagon.

is a pentagon.

Correct Answer:A polygon with 6 sides,is a hexagon.

is a hexagon.

Correct Answer:A polygon with 8 sides,is an octagon.

is an octagon.

Q3.
Which of these are properties of a rectangle?
An image in a quiz
4 equal sides.
Correct answer: Two pairs of parallel sides.
Correct answer: 4 right angles.
Q4.
Look at this pentagon. How many right angles does it have? right angles
An image in a quiz
Correct Answer: 2
Q5.
Look at this hexagon. How many right angles does it have? right angles
An image in a quiz
Correct Answer: 0, zero, none
Q6.
This rectangle has been cut in half using a diagonal line. What shape will both halves be?
An image in a quiz
squares
rectangles
Correct answer: triangles

6 Questions

Q1.
How many pairs of parallel sides does this quadrilateral have?
An image in a quiz
0
Correct answer: 1
2
3
Q2.
The pentagon has been decomposed into three polygons. Match the name of the polygon to the correct letter.
An image in a quiz
Correct Answer:A,triangle

triangle

Correct Answer:B,triangle

triangle

Correct Answer:C,quadrilatral

quadrilatral

Q3.
This hexagon has been decomposed into two shapes. Select the names of the decomposed shapes.
An image in a quiz
Correct answer: pentagon
triangle
rectangle
hexagon
Correct answer: quadrilateral
Q4.
Two lines that meet at a right angle are called __________ lines.
An image in a quiz
parallel
Correct answer: perpendicular
curved
Q5.
Look at the image. Which statements are true?
An image in a quiz
This polygon is a quadrilateral
Correct answer: It has one right angle
It has one pair of parallel sides
Correct answer: It has one pair of perpendicular sides
Q6.
This octagon has been decomposed into 3 polygons. Match each polygon to the correct description.
An image in a quiz
Correct Answer:A,has one pair of parallel sides.

has one pair of parallel sides.

Correct Answer:B,has only two right angles.

has only two right angles.

Correct Answer:C,has more than one pair of perpendicular sides.

has more than one pair of perpendicular sides.