An Alternative Way to Solve a Problem

Essential Question:  How can you develop and test "invented" procedures for solving problems?

CCSS:  2.NBT.7, 7.EE.1, Mathematical practice #2,#3,#7  TEKS: 2.4D, 6.3C, Process Standard G

Grade levels:  2-12

Instructional format:  video, student discussion, group discussion


Supplies:  video, older student note-taker, younger student note-taker

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.

Book Cover

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.

Book Cover

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

Writing Across the Curriculum:
The NumberFix Project


Book Cover

 Wacky We-Search Reports:
A popular book on writing
across the curriculum.