Areas of rectangles and squares

The area of a rectangle is the product of its base and altitude:

[[$ A = a \cdot h $]]

Note! Since the altitude and the base of a rectangle converge, the area of the rectangle can also be calculated as the product of two adjacent sides.

The area of a square is the product of its base and altitude, i.e. the product of two adjacent sides:

[[$A = a \cdot a = a^2$]]

Note! The base and altitude of the square are equal in length.

Example 1

Calculate the area of the tatami mat.

The mat is a rectangle, which means that

[[$ A = a\cdot h = \text{180.0 cm} \cdot \text{90.0 cm} = 16 200 \text{ cm}^2 $]]

The value of 16200 is quite big, so it would be more illustrative to give an answer using a bigger area unit. How do you convert 16200 cm² to square metres?