Åk 6–9
3.1 Rectangle and Squares

Area calculations of a Rectangle

Here is a rectangle with a grid.  Every square/area unit in the grid represents 1 cm².

If you calculate how many area units/squares which are in the rectangle, you see that there are 20 of them.

Instead of counting each square, you can count the number of columns and multiply it by the number of rows, 5 · 4 = 20.
It goes more quickly.

20 area units = 20 cm²

In the last example, we talked about columns and rows.

The columns represent the base of the rectangle.

The number of rows represents the height of the rectangle.

In the figure, we normally don’t have a grid but if you have the measurements you can hopefully calculate the area of the rectangle.

Area: 5 cm · 4 cm = 20 cm²

The rectangles area is equal to the base multiplied by the height.

Area calculations for a Square

Here is a square where the sides are 3 cm long.