Q&A #417

Addition error pattern

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From: Gail (for Teacher2Teacher Service)
Date: Jul 19, 1998 at 14:45:01
Subject: Re: Addition error pattern

Dear Shirley,

I guess I was thinking more about the idea that the student didn't realize 
there were amounts in the ones column that weren't being added.  I do think 
that is part of the problem.  

As for the zero...  does the student do this (I understand that it is a 
hypothetical student) for a zero no matter where it is placed?  Or is it 
only happening in the ones column.  I guess I would start by having the 
student orally explain to me what s/he was doing as s/he added a set of 
numbers.  Then, when s/he put down the zero, incorrectly,I would have an 
idea of why that was happening.  

Perhaps the student saw the teacher add a set of numbers that just happened 
to add up to a multiple of ten, and thinks that you always get a multiple of 
ten.  That is the reason it is important to choose sets of numbers to use as 
examples carefully, since you never know the conclusions children will draw 
from examples.  Not only that, but you must be sure to listen to their 
reasoning, because they might be getting the wrong answer for the right 

So, to say simply, I think that your first step should be to listen to the
student's explanation, since the problem is one of misunderstanding.  Then
you can use place value blocks to prove to the student that a zero doesn't
always belong in the ones place.  You can check for understanding by having
the student generate two sets of numbers, one that will have a sum with a
zero in the ones place, and the other which won't.  Let the student explain

 -Gail, for the Teacher2Teacher service

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