"One, Some or None? Geometry" has a simple premise: if I gave you three clues about a geometric shape, would you be able to draw one, some or no kinds of shapes? This activity raises the bar on critical thinking and combines multi-model types of problem solving, as students draw examples (or non-examples) to support their ideas.
This 40 page packet comes with clues for triangles ("has 2 equal sides," "has a right angle," etc.) and quadrilaterals ("has 1 set of parallel sides," "has 3 right angles," etc.) in different sizes so that you can place them on the board and read them together, or hand them out to small groups of students to work together. There are also homework sheets for students to do at home, as well as "challenges" for your students who need something to really push them.
This is a very versatile activity; you can start off each day in your classroom by choosing 3 clues at random, and then posting them on the board, and then having students write in their journals. Similarly, they can work at math centers where they read 3 cards that you selected and figure out the solution. I've included 10 examples of randomly selected sets of cards, along with their solutions.
I've also included a re-written version of an article that I authored that was included in the NCTM publication "Teaching Mathematics in the Middle School" that appeared several years ago.