What is the formula to calculate the area of a rectangle?

The formula to calculate the area of a rectangle is determined by multiplying the length by the width. This is because the area represents the total space contained within the boundaries of the rectangle. The length measures one side of the rectangle while the width measures the adjacent side. By multiplying these two measurements, you derive the total number of square units that fit within the rectangle.

Option A describes a sum of the length and width, which does not yield the area but rather the perimeter when used in conjunction with the correct formula. Option C provides the formula for the perimeter of a rectangle, as it involves adding both dimensions and then multiplying by 2. Option D, which suggests a difference between length and width, is not relevant in this context and does not represent any geometric property related to the area of a rectangle. Thus, multiplying length by width accurately gives the area, making this the correct formula.