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```Date: 05/05/2003 at 22:29:25
From: Jessica
Subject: Finding a sum

Explain how 10 helps you find the sum of 9 and 8.
```

```
Date: 05/06/2003 at 17:06:22
From: Doctor Peterson
Subject: Re: Finding a sum

Hi, Jessica.

One way to add a pair of numbers like this is to go to ten and then
see how much more is left to add. I'll demonstrate by adding 8 + 5:

We start with 8. That is 2 less than 10, so if we add 2 to the 8, we
get to 10. But we want to add 5; that is 3 more than 2. So after we

Here is a picture:
________5________
/                 \
8                   2         3
+-------------------------------+------>|---------->|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0   1   2   3   4   5   6   7   8   9  10  11  12  13  14

It's a lot easier to think about than to write!

If you have any further questions, feel free to write back.

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
```
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