Calculate the area of a rectangle measuring 13 m by 12 m.

Step-by-step solution

1. 1

   Write down the formula. For any rectangle,

   $A=\text{length}\times\text{width}$

   This works because a rectangle tiles exactly into a grid of unit squares — here $13$ columns by $12$ rows.

2. 2

   Substitute the two measurements.

   $A=13\ \text{m}\times 12\ \text{m}$

   Both measurements are already in the same unit, so no conversion is needed. If one had been given in centimetres, converting first would be mandatory.

3. 3

   Multiply.

   $13\times 12=13\times 10+13\times 2=130+26=156$

4. 4

   Attach the correct unit. Metres times metres gives square metres:

   $A=156\ \text{m}^2$

   The exponent on the unit is not decoration — it records that the quantity is two-dimensional.

5. 5

   Check the result against a nearby estimate. A $13\times 12$ rectangle is slightly larger than a $12\times 12$ square of area $144$ m$^2$ and slightly smaller than $13\times 13=169$ m$^2$. Since $144<156<169\;\checkmark$, the answer is in the right range. For contrast, the perimeter of the same rectangle is $2(13+12)=50$ m — a length, measured in plain metres.