When You Multiply by 10, Just Add a Zero? Horrors!?!



Monday, October 1st, 2018
Have you ever asked students to solve 12.6 x 10, and they respond that the answer is 12.60? I have, many times. Students who do this apply a pattern that works when they multiply whole numbers by 10—they tack on a zero to the end of the number they’re multiplying. But then they apply the same pattern when working with decimals. What can we do?
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When Should and Shouldn’t We Give Answers?



Sunday, February 5th, 2017
Over a year ago, I blogged about The 1–10 Card Investigation. I didn't provide a solution to the problem and no one who commented asked for one. But a newly posted comment requested the solution. That pushed me into a conversation with myself about how I should respond, and about giving answers in general.
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An Oldie Revisited: The Border Problem



Tuesday, April 19th, 2016
Here's one of my favorite oldies. (No, not the photo—the border problem.) I was so pleased to see this math investigation included in Jo Boaler’s latest paper. This blog post presents a detailed lesson plan for using the border problem with students and also includes a five-minute video clip to give you a sense of how the instruction went with one class.

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Can You KenKen?



Thursday, October 1st, 2015
I’ve taught students in grade 2 through middle school how to solve KenKen puzzles. If you’ve never solved KenKen puzzles yourself, or haven't engaged your students with them, read about how I’ve introduced them in the classroom. But be warned: KenKen puzzles can be addictive.




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