# Inside Track: 2-Digit Subtraction with Regrouping

### Teaching Video:

This week, two changes to these worksheet support pages:

1. The worksheets are to help students practice an algorithm, rather than drilling number facts
2. I have added a second video, aimed directly at your students

Please add a comment below, if you like, to let me know what you think.

Subtracting with regrouping is one of the earlier algorithms children learn. Let me make a few recommendations, also discussed on the video:

• Use base ten blocks to illustrate the operation and the regrouping process (see the students’ video below).
• Avoid saying “borrow”, since that is not what is happening. I recommend any of “regrouping”, “trading” or “breaking and making tens”.
• Introduce examples that need regrouping from the beginning, rather than allowing students to do easier examples without regrouping first. This is because students can develop “buggy algorithms” if they work out that you can do subtraction working from left to right by figuring out the difference between the two numbers in each problem, rather than thinking about taking away.
• Use the language “take away”, rather than ” this from that”. Students saying “3 from 8″, etc, may reverse the numbers without realising, and apply it incorrectly when regrouping is required.
• Make sure students have memorized the subtraction number facts before attempting this algorithm, and don’t allow use of a calculator. Otherwise, why would you teach this algorithm at all, since a calculator could to the entire thing in seconds.