Curriculum placement
Grade 3. This describes the skill, not a learner estimate.
Perimeter of a polygon
Find perimeter and missing side lengths
Problem types
- Follow the whole border
- Find a missing side from the border
Builds on
- Adding within 100
- Adding several two-digit numbers · Useful idea
The perimeter of a polygon with many sides adds several lengths.
- Add two-digit numbers · Useful idea
Adding side lengths of two digits finds the distance around a shape.
- Measuring length with equal units · Useful idea
Perimeter measures every side with the same unit and adds the lengths.
- Adding three numbers · Useful idea
The distance around a shape is the sum of its side lengths, so a triangle needs three addends.
Leads to
- Area and perimeter problems
- Expressions with variables · See it applied
Adding side lengths gives a perimeter. With a letter for an unknown side, the same sum is an expression you can evaluate.
- Scale drawings of lengths and areas · See it applied
Scaling a figure by a factor scales its perimeter by the same factor.
Related skills
- Coins and bills · Shared foundations
- Subtracting within 100 · Shared foundations
Open the interactive map to explore lessons and skill connections.