New
New
Year 8

Checking understanding of perimeter

I can find the perimeter of many polygons or compound shapes.

New
New
Year 8

Checking understanding of perimeter

I can find the perimeter of many polygons or compound shapes.

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Lesson details

Key learning points

  1. The perimeter of any polygon can be found by summing the sides.
  2. The perimeter of shapes made from polygons can be found.
  3. Some methods for finding perimeters are more efficient than others.
  4. Missing lengths can be found when the perimeter is known.

Keywords

  • Perimeter - the distance around a 2D shape

  • Polygon - flat (2D), closed figure made up of straight line segments

  • Compound/composite shape - a shape created using two or more basic shapes

Common misconception

Summing all of the given lengths and only the given lengths to find the perimeter.

With each example discuss which lengths are part of the perimeter, which lengths are not and whether any lengths are equal to others.

A pupils to consider other concrete examples of perimeter outside of the classroom (e.g. running a lap around the edge of a sports field).
Teacher tip

Equipment

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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6 Questions

Q1.
Which of these units are a measure of length?
cl
kg
Correct answer: km
m$$^2$$
Correct answer: mm
Q2.
The image shows a wall whose length has been measured in four parts. The total length of the wall is m.
An image in a quiz
Correct Answer: 420, four hundred and twenty, 420m, 420 m
Q3.
Which length is equal to $$a$$?
An image in a quiz
$$b$$
$$c$$
$$d$$
$$e$$
Correct answer: $$f$$
Q4.
A shape is a shape created using two or more basic shapes.
Correct answer: compound
regular
solid
Q5.
Solve the equation: $$20 = 12 + a$$
Correct Answer: 8, a = 8, 8=a, 8 = a, eight
Q6.
Solve the equation: $$2a + 8 = 18$$
Correct Answer: 5, five, a=5, a = 5

6 Questions

Q1.
The is the distance around a 2D shape.
Correct Answer: perimeter, Perimeter
Q2.
Which of the units could be used to measure perimeter?
Correct answer: cm
cm$$^2$$
cm$$^3$$
Q3.
What is the perimeter of the rectangle?
An image in a quiz
7 m
10 m
12 m
Correct answer: 14 m
Q4.
When $$a = 5$$ the perimeter of the octagon is mm.
An image in a quiz
Correct Answer: 40, forty, 40 mm, 40mm
Q5.
The perimeter of the hexagon is 24 cm. Find the value of $$a$$.
An image in a quiz
Correct Answer: 4, four, a = 4, a=4
Q6.
The perimeter of the compound rectilinear shape is cm.
An image in a quiz
Correct Answer: 180, one hundred and eighty, 180 cm, 180cm