Lesson: Show the video above. The video is of a second grader that developed his own method for solving subtraction with regrouping (or borrowing). The video cues younger students to replicate the method that they see by trying it on a few problems. Then, ask the children to compare methods - which is easier for them to remember, why do you think Donald's method works, etc. Have younger students use the following note-maker to keep track of their work. For older students - can they prove why Donald's method always works? This is a proof that requires the use of negative numbers, so early secondary students could prove showing each step with representative negative numbers, while older secondary students could write a proof using variables, operations, and properties. Have students use the following note-maker to keep track of their work.

Extension/follow-up: Have students try to create their own original procedure for any mathematical process, such as adding multi-digit numbers or even adding/subtracting fractions. Have them present their "new" method and then use classmates to test (or prove) their procedures.

Help Wanted on Mont Vernon This book combines history and mathematics with adorable characters to teach kids about the many talents of the first U.S. President.

The UnderAchievers: Woven into a fun story, this book provides excellent math lessons for kids.