Simple Math Formulas for Kids: How to Do Simple Math

Elementary Math Formulas

First, let's discuss what a 'formula' is. You can think of formulas as rules that tell you the process for figuring something out. That 'something' might be the area of a square or the volume of a rectangle. You put certain characteristics (such as length and height) into the formula and then perform the operations that the formula specifies.

Perimeter

One of the first elementary math formulas you'll learn is for perimeter, which is the distance around the outside of a 2-dimensional shape. For squares, the formula is P = 4 x s, where 's' is the length of one side. To find a square's perimeter, just replace the 's' with the length of one side and then multiply by four. For instance, if each of the square's sides is two centimeters long, multiply 2 x 4 to get a perimeter of eight centimeters.

For rectangles, you'll find perimeter by simply adding together the four side lengths (P = l + l + w + w). If the rectangle has two sides that are three inches long and two sides that are five inches long, you'll add 3 + 3 + 5 + 5 to get 16 inches. Note that you can also multiply each of the side lengths by two and then add those products together to get the same answer: P = (2 x l) + (2 x w) = (2 x 3) + (2 x 5) = 6 + 10 = 16.

Area

Area is the amount of space a shape covers. For squares and rectangles, you find it by multiplying length by width (A = l x w). Since a square's length and width are the same, you'll just multiply the length of one side by itself. For instance, if the square's sides are all one meter long, you'll multiply 1 x 1 to get the area of one square meter.

For rectangles, you'll multiply the length of one of the shorter sides by the length of one of the longer sides. For instance, if a sheet of paper is ten centimeters long and eight centimeters wide, its area is found by multiplying 10 x 8 to get 80 square centimeters.

Volume

Volume tells you how much space is taken up by a 3-dimensional object, like a cube. It's usually found by multiplying length, width and height (V = l x w x h). For example, a cube with a height of three centimeters will also have a length and width of three centimeters. This means its volume is found using this calculation: 3 x 3 x 3 = 27.