Full issue PDF of Arithmetic Teacher volume 28, number 4 (December 1980).
This article is available to members of NCTM who subscribe to Teaching Children Mathematics. Don't miss out—join now or upgrade your membership. You may also purchase this article now for online access.
Putting a twist on a popular mathematical tool, this collection of activities shows how putting a number 1 in the bottom-left cell and a 100 in the top-right cell can better support student reasoning.