Paper FoldingElementary and Middle School
The idea of this activity is to use paper folding to build intuition about multiplication, division, and factoring. Students learn how to fold strips of paper into 2 and 3 equal parts and then discover that they can make any other number that is a multiple of 2's and 3's by combining folds.
Estimating RatiosElementary and Middle School
This is a simple game that can lead to a lot of valuable conversation about ratios and fractions. The game is easy to create using dynamic geometry software, and works especially well if it can be projected onto a board so that students can do it as a group.