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Year 10
Higher

Checking and securing understanding of polygons

I can recognise and name polygons with five or more sides and recognise the difference between regular and irregular shapes.

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New
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Year 10
Higher

Checking and securing understanding of polygons

I can recognise and name polygons with five or more sides and recognise the difference between regular and irregular shapes.

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Share activities with pupils
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Lesson details

Key learning points

  1. The prefix is derived from Ancient Greek.
  2. A regular polygon has sides that are all equal and interior (inside) angles that are all equal.
  3. An irregular polygon has sides that are not equal or interior (inside) angles that are not equal.

Keywords

  • Polygon - A polygon is a flat (2D), closed figure made up of straight line segments.

  • Regular - A regular polygon has sides that are all equal and interior (inside) angles that are all equal.

  • Irregular - An irregular polygon has sides that are not equal or interior (inside) angles that are not equal.

Common misconception

The name for a shape only applies to the regular version of that shape. E.g. An irregular pentagon is just a shape, as pentagons must have 5 equal sides.

The name of a shape is known based on the number of sides and these do not have to be regular.

If appropriate, consider playing a game where pupils have to draw a named shape and they earn a point if they draw a different picture from the teacher. The teacher should always draw the regular version of the shape.
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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

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Starter quiz

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6 Questions

Q1.
An equilateral triangle has __________ equal angles.
no
two
Correct answer: three
Q2.
A rhombus always has __________.
four angles of equal size
four angles of different size
Correct answer: four sides of equal length
four sides of different length
Q3.
A rectangle always has __________.
Correct answer: four angles of equal size
four angles of different size
four sides of equal length
four sides of different length
Q4.
A square always has __________.
Correct answer: four angles of equal size
four angles of different size
Correct answer: four sides of equal length
four sides of different length
Q5.
A square has length 5 cm. Its perimeter is cm.
Correct Answer: 20, twenty, 20 cm, 20cm
Q6.
A rhombus has a base of length 5 cm. Which statement is true about its perimeter?
Its perimeter is less than 20 cm.
Correct answer: Its perimeter is equal to 20 cm.
Its perimeter is more than 20 cm.

Exit quiz

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6 Questions

Q1.
A polygon has sides that are all equal and interior (inside) angles that are all equal.
Correct Answer: regular
Q2.
An polygon has sides that are not equal or interior (inside) angles that are not equal.
Correct Answer: irregular
Q3.
Which quadrilaterals are always regular?
parallelograms
rectangles
rhombi
Correct answer: squares
trapezia
Q4.
Why is the octagon in the image not regular?
An image in a quiz
Not all of its interior angles are the same size.
Correct answer: Not all of its sides are the same length.
Both of the above.
Q5.
The perimeter of the heptagon is cm.
An image in a quiz
Correct Answer: 70, seventy
Q6.
A circle is __________.
a regular polygon
an irregular polygon
Correct answer: not a polygon