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### Fact Families

```
Date: 09/21/2000 at 14:17:20
From: Ann Treacy
Subject: Fact Families

What is a "fact family?"
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```
Date: 09/21/2000 at 17:50:58
From: Doctor Rick
Subject: Re: Fact Families

Hi, Ann.

A fact family can be FOUR -- FOUR -- FOUR facts in one!

When you memorize an addition fact like 2 + 3 = 5, three other facts

2 + 3 = 5
3 + 2 = 5
5 - 2 = 3
5 - 3 = 2

Some fact families have only two members. For instance,

2 + 2 = 4
4 - 2 = 2

Multiplication and division facts come in families in just the same
way. For instance,

3 * 5 = 15
5 * 3 = 15
15 / 3 = 5
15 / 5 = 3

These are things we knew, but they didn't teach the term in school
when I was a kid. It's a good term, though, I think.

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