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Place value and 2x2 multiplication


Mommy22alyns
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Rebecca's not getting it all the time. :glare: When the concept was introduced, she breezed through it, working all the extra problems on the board flawlessly. Now she's struggling with every 2x2 problem and constantly, constantly forgetting to put that placeholder 0 in there. I printed her out some extra problem sheets and tried to break things down on the board like this:

 

78x32 = 78x2 + 78x30

 

This was today, so I don't know how much of a dent this has made. It looks like a place value misunderstanding, right? Is there anything else I can do but keep going over it and practicing?

 

:willy_nilly:

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Instead of doing the standard algorithm where you start with the ones and go on to the tens, have her start with the tens. Then have her start with the ones on the next problem. Then show her 3x3 multiplication and have her mix up which place she starts with.

 

Using manipulatives (base 10 blocks) can help too.

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Rebecca's not getting it all the time. :glare: When the concept was introduced, she breezed through it, working all the extra problems on the board flawlessly. Now she's struggling with every 2x2 problem and constantly, constantly forgetting to put that placeholder 0 in there. I printed her out some extra problem sheets and tried to break things down on the board like this:

 

78x32 = 78x2 + 78x30

 

This was today, so I don't know how much of a dent this has made. It looks like a place value misunderstanding, right? Is there anything else I can do but keep going over it and practicing?

 

:willy_nilly:

 

And I did not ever refer to the zero as a place holder. It is not a place holder. It represents that you have zero ones. You are multiplying by 10, 100, etc. in those lines, so you will have no ones in that answer.

 

ETA: Have you read Knowing and Teaching Elementary Mathematics. The misunderstanding of place value in multiplication with large numbers was covered in the book, with the American teachers talking about place holders and how you could put anything there to just hold the place. I think some teachers even told the kids they could put stars or happy faces instead of zeros!? :001_huh: :willy_nilly: :001_rolleyes::svengo:

Edited by Alte Veste Academy
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And I did not ever refer to the zero as a place holder. It is not a place holder. It represents that you have zero ones. You are multiplying by 10, 100, etc. in those lines, so you will have no ones in that answer.

 

ETA: Have you read Knowing and Teaching Elementary Mathematics. The misunderstanding of place value in multiplication with large numbers was covered in the book, with the American teachers talking about place holders and how you could put anything there to just hold the place. I think some teachers even told the kids they could put stars or happy faces instead of zeros!? :001_huh: :willy_nilly: :001_rolleyes::svengo:

 

 

Sorry, I never told her "placeholder," it was just my off the cuff word while posting. I really should read that book, shouldn't I?

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