Video assignment 3: The transition lesson for teaching 3-digit subtraction by demonstrating and explaining

Your task: On video (recorded in Jing or something equivalent), record yourself demonstrating how to subtract 3-digit numbers as a lesson in the transition phase:

• Make up a problem where you subtract two 3-digit numbers, where you need to trade (regroup) twice.
• Show what to do with the manipulatives, and then show how to write down that step with numbers. Continue going back and forth between manipulatives and numbers at every step.
• Talk as though you are explaining each step as you go. You may either just give verbal explanations of each step or you can simulate a discussion with "students"

Watch out for the language you use to describe the subtraction step: unlike addition, the numbers in a subtraction problem play different roles: the minuend and the subtrahend should be described differently. For example, 7-4 can be read out loud as:

• 7 minus 4
• 7 take away 4
• take 4 from 7

7-4 can't be read the other way around. 4 minus 7, 4 take away 7 and take 7 from 4 all mean something different from 7-4

Things I will take into consideration as I grade this:

• Did you choose a good problem? A good problem should have two steps where you regroup, and it should also have a variety of digits (your explanation will be more clear if you don't have too many 3's in your problem).
• What language are you using for exchanging? You can use trade, exchange, regroup, rename or make, you should not be using "carry".
• Are you using place value language? If you have 4 in the tens place, that number represents 4 tens or 40, but it is not simply 4.
• Are you effectively going back and forth between the manipulatives and the numbers? You should be using the manipulative steps at each stage to explain the numerical steps.

It's been a while since we did this in class, so here are a couple of examples of what I want to see:

Example 1 (example 2) Example 3

This video is due on Monday 11/28