To fence a vegetable garden, you need to know how much wire goes around it. To plant, you need to know how much floor is inside. There are two different measurements: the perimeter and the area.

Perimeter: the path around

DefiniçãoPerimeter

The perimeter is the measurement of the contour of a figure: it is the sum of the lengths of all sides.

An ant that goes around a rectangular table measuring 2 m by 1 m walks 2 + 1 + 2 + 1 = 6 m. This is the perimeter of the table.

Area: how much can fit inside

DefiniçãoArea

The area is the measurement of the surface of a figure. In the mesh, we count how many squares cover the figure. If each square has 1 cm on a side, the area is given in square centimeters (cm²).

Click on the squares to create a figure. Compare the rectangle 3 × 4 with the long strip of 12 squares.

A shortcut for rectangles

In a rectangle of 3 rows with 4 squares each, there is no need to count them one by one: there are 3 × 4 = 12 squares. The area of ​​the rectangle is length × width.

AtençãoSame area, different perimeters

The rectangle 3 × 4 and the strip 1 × 12 have the same area (12 little squares), but different perimeters: 14 and 26. Therefore, to fence a vegetable garden of the same area, the more “square” shape uses less wire.

Check the answer

The sides need to add up to 8 (half of 16): 1 × 7 (area 7), 2 × 6 (area 12), 3 × 5 (area 15), and 4 × 4 (area 16). The square 4 × 4 has the largest area.

True or false?

  1. The perimeter of a square with side 5 cm is 20 cm.
  2. Figures with the same area always have the same perimeter.
  3. A rectangle measuring 4 cm by 3 cm has an area of ​​12 cm².
  4. Area and perimeter are measured in the same unit.