As Mr. McCabe was helping a 3rd grader with her homework, he suddenly looked flummoxed. What was this young lady doing? The 3rd grader went on to show Mr. McCabe how she utilizes regrouping to solve the subtraction problem. Mr. McCabe, quite perplexed, went on to show the young lady how he learned to subtract in Scotland. Below is an image of Mr. McCabe's work.
Here are two examples of an individual solving a subtraction problem using Mr. McCabe's strategy.
Questions to Consider
Describe, in your own words, what Mr. McCabe does to solve the subtraction problem.
What makes Mr.McCabe's strategy work?
Is his strategy more or less efficient than traditional regrouping? Why or why not?
Try your hand at it. Solve several of your own subtraction problems using the McCabe strategy.