EN
BuilderGrades 3–4⏱ 15 min

Area and perimeter

Stretch a rectangle on a grid: count the squares inside, walk around the edge, and solve shape puzzles.

Standards: 3.MD.C.73.MD.D.84.MD.A.3

1Wonder

You are building a garden. You need a fence to go around it and soil to fill it. Are those the same measurement?

2Explore

Area and perimeter

This activity needs a bigger screen

Turn your phone sideways, or open this lesson on a tablet or computer. The explanation and quiz below work here.

123456789101112131415Area5 × 3 = 15square unitsPerimeter2 × (5 + 3) = 16unitsSillyChili
Width
5
Height
3
Try this
  • Make a 4 × 3 rectangle. Count the squares inside. Then press Walk around it.
  • Find two different rectangles with area 12. Do they have the same perimeter?
  • Press Next challenge and solve all four challenges.
  • Which rectangle with area 16 has the shortest fence?

3Explain

12345678910111213141516P = 16SillyChili
Step 1 of 5

Perimeter: the distance around

Walk all the way around the edge and count the unit steps: 16. The perimeter is the length of the fence.

For a rectangleArea=w×hPerimeter=2×(w+h)\text{Area} = \htmlClass{c-green}{w \times h} \qquad\qquad \text{Perimeter} = \htmlClass{c-blue}{2 \times (w + h)}

4Practice

Question 1 of 5

What is the area of this rectangle?

square units

5Recap

  • Perimeter is the distance around a shape. It is a length (cm, m).
  • Area is the space inside, counted in unit squares (cm², m²).
  • Rectangle: area = width × height; perimeter = 2 × (width + height).
  • Shapes with the same area can have different perimeters. Squares have the shortest perimeter for their area.