# Monthly Archives: May 2009

## Notes on Operations – Unary Minus

“Unary minus” is the name for the symbol in , which looks like a minus, but isn’t a subtraction of two quantities.  This simple-looking thing is associated with lots of confusion in middle school math. We’re all familiar with “-” … Continue reading

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## Problems in Algebra – part 2

In this series on common mistakes made by students in middle school mathematics, let’s look at this one: Problem: Simplify Jessica’s response: . We can agree that this is wrong, and we can probably tell the student what to do … Continue reading

## Problems in Algebra – part 1

On the heels of the series of posts on multiplication, I’d like to look at particular problem areas in middle school mathematics that show up year after year.  Kids make mistakes or have difficulties, each in their own unique way, … Continue reading

## What is Multiplication – the Series

Here’s a summary of the series (thus far) of posts on multiplication, with links. This allows you to read them in order, from oldest to most recent. The series grew from a concern raised in the post Middle School Math … Continue reading

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## What is Multiplication – part XIII

Time for some wrap-up and some pulling together, after twelve prior installments in this series.  This doesn’t mean that I think I have arrived at some kind of eternal truth about multiplication.  Instead, the whole premise of this work is … Continue reading

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## What is Multiplication – part XII

In this post I sliced the various ways we’ve looked at multiplication into two basic types, which I called scalar multiplication and unit multiplication.  This is not the only useful way to slice and dice the various multiplicative structures we’ve … Continue reading

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## Tally Marks and Roman Numerals

In earlier posts on tally marks, I mentioned that one of the drawbacks of tally marks as a representation system for numbers is that it isn’t easy to copy numbers from one place to another.  In our normal use of … Continue reading

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## What is Multiplication – part XI

We’re arrived at the eleventh installment of this series, and it would be worth asking whether we have arrived at any conclusions yet about what multiplication really is.  We’ve seen multiple manifestations of the idea of multiplication, and it would … Continue reading

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