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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

Hey everyone...I have a little question : How do you factorise big numbers ?

I could just use my calculator but that would be too long... Is there any technique known that I could use ? Take this number : 2016. I must put it in a tree of factors... But there's too many possibilites ..

Thanks !

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 100,366

Hi;

For a number like 2016 you use trial division. Do you know how?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **Thinking is cheating.**

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

Mmmh.. An example would be helpful. I already have the prime numbers of 2016. Would that be helpful to find the others ?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 100,366

Are you looking for the divisors?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **Thinking is cheating.**

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

Well, basically, I have the number 2016 and must find its factors in a tree of factors. Could you show me how to proceed ? I don't know if my question is clear^^

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 100,366

Hi;

What do you mean by a tree of factors. Got a web page with a picture?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **Thinking is cheating.**

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

I have 2016, the prime numbers at the end, now I need to find the others... I'll be creating you a diagram,

I can't post a link

*Last edited by Al-Allo (2012-08-23 08:16:18)*

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 100,366

Seen this page?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **Thinking is cheating.**

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

No, but that's what I'Ve been talking about. I have all the prime numbers, but I don't know how to find the others....

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 324

I know that 2016 = 2 exponent 5 . 3 exponent 2 . 7

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 100,366

Did you try that page? It is self explanatory.

Here is what wolfram does. Okay, where did he go? One second he was here and the next, The Twilight Zone!

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **Thinking is cheating.**

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,444

hi Al-Allo

2016 is even so divide out a 2.

Keep doing this until you end up with an odd number.

There are some other tricks for finding some factors. Do you want to know these?

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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