**A number model is a sentence that shows how a series of numbers are related.** An example of a basic number model could be 12+3=15.

A number model is an equation that incorporates addition, subtraction, multiplication and division, which are used singularly or together. In an equation, the symbols for these functions will be listed as, "+," "-," "*" and "/." As long as each part of the equation is related using some kind of sign, the equation is considered a number model.

In order to be a number model, an equation must show equality. For example, the equation, "8 + 1" is not a number model because it lacks the equal sign. However, "8 + 1 = 9" is a number model.

Number models can also be used to discover the perimeters and area of shapes. These types of equations may be in numeric or word form. To find the area of a square, when "a" is the length of one side, the number model would be written as: "area = a * a." Notice that in this example, there is a multiplication sign and an equal sign present.