Perimeters of polygons
Solve problems involving perimeters of polygons: find perimeter from side lengths, find an unknown side length, and explore rectangles with same perimeter but different areas (or vice versa)
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Teaching Table
Set out your lesson
“If a rectangle has a perimeter of 24 cm and one side is 8 cm, can your child work out the length of the other side — without drawing it?”
Full guide and materials
- Activity. Solve problems involving perimeters of polygons: find perimeter from side lengths, find an unknown side length, and explore rectangles with same perimeter but different areas (or vice versa)
What to notice. Calculate the perimeter of a rectangle with sides 8 cm and 5 cm • Find the missing side of a pentagon with perimeter 30 cm and four known sides • Draw two rectangles both with perimeter 24 cm but different areas
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1 approach
If a rectangle has a perimeter of 24 cm and one side is 8 cm, can your child work out the length of the other side — without drawing it?
Solve problems involving perimeters of polygons: find perimeter from side lengths, find an unknown side length, and explore rectangles with same perimeter but different areas (or vice versa)
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Check understanding
- Calculate the perimeter of a rectangle with sides 8 cm and 5 cm
- Find the missing side of a pentagon with perimeter 30 cm and four known sides
- Draw two rectangles both with perimeter 24 cm but different areas
“If a rectangle has a perimeter of 24 cm and one side is 8 cm, can your child work out the length of the other side — without drawing it?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Measurement
- Age range
- Ages 8–9