When calculating the perimeter of a rectangle, which formula should be used?

To calculate the perimeter of a rectangle, the appropriate formula is 2 times the sum of the length (l) and the width (w). This is represented mathematically as 2(l + w). The reasoning behind the formula is that the perimeter is the total distance around the rectangle, which consists of two lengths and two widths.

By adding the length and width together (l + w), you are finding the total distance of one complete set of opposite sides. Multiplying this sum by 2 accounts for both pairs of opposing sides, thereby giving you the total perimeter. This formula is essential in geometry and practical scenarios where determining the surrounding boundary of a rectangular area is necessary, such as fencing or borders.

The other options provided do not correspond to the calculation of a rectangle's perimeter. The multiplication formula and the circular measurement both relate to different geometric shapes, while the option that adds A and B is not applicable to finding perimeter as they represent different mathematical operations and dimensions.