Which formula is used to calculate the area of a rectangle?

The area of a rectangle is calculated using the formula that involves multiplying the length by the width. This formula works because the area represents the total space within the rectangle. By taking one dimension (length) and multiplying it by the other dimension (width), you can effectively count how many unit squares can fit inside the rectangle.

In this scenario, the other options represent different concepts. The formula that includes ½ bh is used for calculating the area of a triangle, where "b" refers to the base and "h" the height. The third formula involving πr² is for the area of a circle, where "r" is the radius. Finally, the option that lists b + h does not correspond to any area formula but rather appears to only sum the base and height without considering the necessary multiplication to find area. Thus, the length multiplied by the width is the correct and standard approach to determine the area specifically for rectangles.