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## Number Theory & Primes

Activities with Number Theory and Primes

## Sum Primes

To view the Prime Chart, click HERE. The concept of prime number is one that has fascinated mathematicians and frustrated students for a long time. It is one of the most fertile fields where one can make interesting discoveries on any level one wishes. By way of illustrating this, you only have to check out [...]

## Big Primes

Preface: On this page I present a series of three handout sheets that I use in my Pre-algebra classes whose purpose is to teach how to find out if a large number is a prime or not. And by “large”, my main concern, as you will soon see, are numbers greater than 100 and less than 10,000. [...]

## Divisibility Tests

Knowing quickly whether one number is divisible by another is a basic math skill which is very useful and serves many purposes as one studies mathematics at all levels, high or low. For many readers, this page will contain much information that you already know, but I think if you will bear with me, you will [...]

## Egyptian Math

In this page, WTM is going to travel back in time and do some really “old-fashioned” mathematics. Specifically we will look at how the ancient Egyptians multiplied quantities and dealt with fractions. To make things more convenient for our discussion, we will use our own numbering system and symbols. This is a piece of good news/bad [...]

## Repeating Decimal Patterns

Many years ago I read some interesting articles in a British school mathematics journal about the various patterns that can be found in the decimal expansions of repeating decimal forms of certain rational numbers [aka fractions]. So I began my own investigation of this topic to see what I could discover on my own. Below [...]

## PAUL ERDÖS: a tribute

[Note: The story below was excerpted from an article that appeared in the Chicago Tribune, "Erdös left a whole world of survivors", written by Charles Krauthammer in the Fall of 1996. For a more lengthy account of his life, click here. For information about an interesting book about his career, click here.] Paul Erdös was his [...]

## It’s a Square, Square World

Square numbers are very important in mathematics, and virtually at all levels from arithmetic, to algebra, geometry, calculus and statistics. So I feel young students should be exposed to them as early as possible, and that some of them should be memorized right along with the “times tables”. In fact, at the grade I teach (7th [...]

## Rep-Digit Numbers

This is a math activity that needs you to use your best investigation skills. So get out your paper and pencil and put on your thinking cap. (And you may wish to consider a calculator, but it won’t be of much use some times.) Definition Let a rep-digit number be any number that consists of a [...]

## Primes and Square Pairs

[Preface: This math activity is meant to be done slowly, and in parts, so as not to reveal the "secrets" too soon. And, though there is an answer section at the end, you are encouraged to "work things out first" so you will gain full advantage of the concept.] Part I Here is an interesting [...]

## Sexy Primes

HOW ABOUT SEXY NUMBERS! Before you begin to think that this page of WTM is going to be “x-rated”, we urge you to put that thought out of your mind right now. You see, we have merely created a new category for classifying numbers. (We assure you that we’re not going to talk about boy-numbers [...]