There are four basic operations in mathematics:
These operations define actions. They are not static statements, but dynamic interactions between quantities.
Subtraction can be thought of in two ways: as a removing or taking away of a quantity, or as a comparison, or seeing a difference between two quantities. In the take-away model, a quantity is actually removed from the beginning group:
The models are simple, yet powerful. They will work for operations with fractions, decimals, and signed numbers, as well as algebraic operations. We'll learn more about those in future lessons.