Final answer:
Multiplying the width by the length of a rectangle gives you the area of the rectangle, which is a measure of its two-dimensional space in square units.
Step-by-step explanation:
When you multiply the width by the length of a rectangle, you are calculating its area.
Units can be a helpful way to think about these concepts. For example, if we say a rectangle has a width of 3 meters, then the units for the area would be in square meters because we are covering a two-dimensional space. Therefore, dimensionally, area involves units squared, like meters squared (m²).
Conversely, the perimeter is the total distance around the rectangle, and it would not make sense for the units to be squared since we are only measuring a line around the figure, which has a dimension of length. If we think about a rectangle that has all sides of length 'a', the perimeter would be calculated as 4a, which is simply a linear measure, not an area.