Open Middle was co-founded by Robert Kaplinsky and Nanette Johnson and you can find so many Open Middle exercises on http://www.openmiddle.com. I really enjoy these types of problems and just watching my students try these exercises is very rewarding because there’s just so much thinking and justification happening.
Here are a couple Open Middle exercises that I made for them:
Even if you don’t use these specific exercises, I highly recommend looking at http://www.openmiddle.com for a couple exercises to use in your class. Students being engaged is a plus, but more importantly it helps build better understanding about the topic at hand.
Let me know if you use these specific exercises! Thanks for reading.