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20
Add four equal sides.
Class 3 · English Medium · Cambridge · Mathematics
Perimeter, shapes, angles and symmetry
Explore perimeter, shapes, angles and symmetry with an example and your own answers.
About this lesson and its coverage
Original Kidemy foundation practice · Read the example, write your answers, then check. This starter is shared across class versions; it is not a complete board-specific lesson or course.
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Learn the idea
Perimeter is the distance around a shape. A right angle is a quarter turn. A symmetry line divides a shape into matching reflected halves.
Worked example
A rectangle 6 cm long and 3 cm wide has perimeter 6 + 3 + 6 + 3 = 18 cm.
- Read the example and explain which rule or evidence it uses.
- Try each task yourself, then compare the answer and its reason.
Your written practice
Show your working on paper. Check your answer, then choose Next.
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4
Each of its four corners is a right angle.
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18
Add two lengths and two widths.
Take it further
Apply the idea in a new situation and explain your method. Open writing needs a guardian or teacher to review it.
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26
Add both lengths and both widths: 2×(8+5).
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7
Divide the perimeter into four equal sides.
Write in your own words. A guardian or teacher should review this response.
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A 5 cm by 3 cm rectangle and a 6 cm by 2 cm rectangle each have perimeter 16 cm.
Check two different pairs with length plus width equal to eight.
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