I don't understand how to work out what a prime number is

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A prime number is a positive whole number (natural number) which cannot be divided into smaller whole numbers. In short, it can only be divided (integer division) by itself and 1.

First prime number is 2, then 3, 5, 7, 11, 13, 17, 19,

To generate a list of prime numbers the Greek Eratoshenes used a method called now the sieve Eratosthenes.

- Write all the natural numbers up to some chosen limit (100, 259, any limit )
- Remove 1 by crossing it ( 1 is no longer considered prime).
- The first prime number is 2.
**Circle the number 2.** - Go through the
**whole list**crossing out all the numbers that are multiple of 2, that is 4, 6, 8,10,12, ... - Repeat.
- The next prime number is 3 since it was not crossed out as a multiple of 2.
**Circle 3.** - Go through the
**whole list**crossing all the numbers that are multiples of 3, and which have not already been crossed out as multiples of 2 . - Number 4 has been crossed out already.
- Next prime number is 5.
**Circle 5** - Go through the
**whole list**crossing all the numbers that are multiple of 5 and which have not been crossed out already as multiples of 2, or 3 - Repeat:
- Next prime number is 7.
**Circle 7** **Go through the whole list again, crossing out the multiples of 7, and so on.**

Enjoy.

Posted on Nov 26, 2013

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Posted on Jan 02, 2017

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Jan 10, 2015 | Roku Televison & Video

Presume you know that prime number is divisible only by itself. See here:

http://primes.utm.edu/lists/small/1000.txt

http://primes.utm.edu/lists/small/1000.txt

Oct 13, 2014 | Computers & Internet

A prime number is a whole number greater than one which has no divisors except one and itself. A composite number is a whole number greater than one that isn't prime, that is, a product of two or more whole numbers. See http://en.wikipedia.org/wiki/Prime_number

Jul 07, 2014 | Computers & Internet

It is any number only divisible by itself and 1 (giving whole number results). A list here of the first 1000

http://primes.utm.edu/lists/small/1000.txt

http://primes.utm.edu/lists/small/1000.txt

May 07, 2014 | Computers & Internet

Prime numbers are those numbers (greater than 1) that cannot be divided by any
number except themselves and one.

The Greek Eratosthenes created a method to find out these prime numbers, although it only worked over a limited range:

1) Write out the numbers from 1 to 100 in ten rows of 10.

The Greek Eratosthenes created a method to find out these prime numbers, although it only worked over a limited range:

1) Write out the numbers from 1 to 100 in ten rows of 10.

2) Cross off number 1, because all primes are greater than 1.

3) Number 2 is a prime, so we can keep it, but we need to cross off the multiples
of 2 (i.e. even numbers).

4) Number 3 is also a prime, so again we keep it and cross off the multiples
of 3.

5) The next number left is 5 (because four has been crossed off), so we keep
it and cross of the multiples of this number.

6) The final number left in the first row is number 7, so cross off its multiples.

7) You have finished. All of the "surviving" numbers (coloured in
white below) on your grid are prime numbers.

Oct 23, 2011 | MathRescue Word Problems Of Algebra Lite

I beleive its-- 67 and 71, good-day! prime numbers are a number that cant be divided equally.

Aug 25, 2011 | Home

No not all odd numbers are prime numbers. A prime number is one that cannot be divided equally by any other number then itself or 1. Therefore numbers such as 9 is not a prime number because it can also be evenly divided by 3Hope this answers your question. Thank you.

Aug 15, 2011 | Home

"Prime Factorization" is finding **which prime numbers** multiply together to make the original number.

Example : What are the prime factors of 12 ?
It is best to start working from the smallest prime number, which is 2, so let's check:

12 ÷ 2 = 6

Yes, it divided evenly by 2. We have taken the first step!

But 6 is not a prime number, so we need to go further. Let's try 2 again:

6 ÷ 2 = 3

Yes, that worked also. And 3 **is** a prime number, so we have the answer:

**12 = 2 × 2 × 3**

As you can see, **every factor** is a **prime number**, so the answer must be right.

Note: **12 = 2 × 2 × 3** can also be written using exponents as **12 = 22 × 3**

Jun 22, 2011 | Computers & Internet

Hey i found this great new site offering Adobe Photoshop Cs2 serial numbers, here's the link:

**Adobe photoshop cs2 serial numbers**

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Jun 03, 2011 | Adobe Photoshop CS2 for PC

I wrote this program for you. You can see it here: pastebin

You should understand how this works and make your own. That way you'll remember it and gain some experience. Not to mention satisfaction.

You should understand how this works and make your own. That way you'll remember it and gain some experience. Not to mention satisfaction.

Apr 10, 2009 | Microsoft Computers & Internet

Oct 23, 2017 | Xerox Office Equipment & Supplies

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