This worksheet is working on subtracting a one digit number from a two digit number. This worksheet has the students focus on regrouping. The idea of this worksheet is to explore what it means to regroup. I like how this worksheet shows the tens block becoming 10 individual ones.
A question I would ask my students would be: Can you draw what the base ten blocks are doing for numbers 1-4.
I would ask them to draw what is happening because this would show me that they understand what it means to regroup. I have found in my placement that students do not understand that when you subtract 1 from the tens place you are subtracting one group of ten.
I would also have my students explore the "Explain it" section of this worksheet. I think often times this section is overlooked because it would cause my teacher to take the time to discuss this with the class. I think many teachers find it easier to teach the method rather than the reason.
Another way I would further my students thinking would be to mix up subtraction problems that require regrouping and ones that do not. Ex. 62-2=? I would use this problem because students might want to regroup because they see 2 and 2. I would use 63-4=? this would cause them to regroup. I would also use 68-4=?
I agree that the explain question, "How can this regrouping idea help you in the first place?" is really the key question. Else, as you explain based on your experience, students might regroup or borrow within every subtraction problem they see even when it is appropriate. The conversation of "Why is this strategy / procedure useful?" is the key question and conversation that should be had soon rather than later in the context of every piece of mathematical content.
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