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Grade 3 Math · World 8: Area and Perimeter Park · Level 76
Perimeter of Polygons
Find perimeters, and a missing side when the perimeter is known.
Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.
What children learn in Level 76
- A polygon is a flat shape with straight sides. Its perimeter is all of its sides added up.
- 5 + 4 + 6 + 4 + 3 is 22, so the perimeter is 22 centimeters.
- If you know the perimeter, you can find a missing side. The perimeter is 22 cm. The sides we know add up to 16, so the missing side is 22 − 16 = 6 cm.
- In a rectangle, opposite sides are equal. Only two are marked, but the perimeter is 6 + 4 + 6 + 4 = 20.
- A regular polygon has all its sides equal. This regular hexagon has 6 sides of 5 cm: 6 × 5 = 30 cm.
Georgia's K-12 Mathematics Standards:
- 3.GSR.8.1 — Determine the perimeter of a polygon and explain that the perimeter represents the distance around a polygon. Solve problems involving perimeters of polygons.