This app provides a platform for students to play with the ideas of negative numbers, including both addition and subtraction. The primary assumption is that, for any positive number, such as 1, there is an inverse, -1, with respect to addition, so that 1 + (-1) = 0. Zero is usually called the additive identity; the inverses are called additive inverses. In the app, a blue ball represents a positive one; a red ball represents a negative one. A blue ball plus a red ball thus results in zero, namely, they cancel out when they come close to each other. This is a useful strategy to learn and teach the big ideas behind negative numbers.
Of course, there are always other ways to explain subtraction as well as negative numbers, each with its own advantages and disadvantages. Ultimately, students should come to the understanding that, given two numbers A and B, (A - B) is a number C such that (C + B = A), whether they are positive or negative.
This app is designed by Dr. Lingguo Bu ([email protected]
) at Southern Illinois University using MIT App Inventor. It is free and ad-free for educational purposes. The author is solely responsible for the errors herein.
Improved checking function and performance involving subtraction; added verbal feedback.
Enabled sensor-driven orientation and improved pair generation algorithm.