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**RadioBoy****Member**- Registered: 2012-12-19
- Posts: 1

Hello, I have just joined the math is fun forum. I expect interesting things here and will also share my experience of math. For example, the miracle of digit 9. The product of digit nine in interaction with itself will always be nine (9 x 9 = 18 = 1+8 =9).

If you are thinking of switching or using alternative energy in your home, solar power is the best choice that can sustain your lifestyle.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,796

Hi RadioBoy

Welcone to the forum!

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 91,471

Hi RadioBoy;

Welcome to the forum.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 15,356

Hi RadioBoy,

**Welcome to the forum!**

Character is who you are when no one is looking.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,558

Welcome!

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**mathaholic****Member**- From: idk
- Registered: 2012-11-29
- Posts: 2,903
- Website

Belated welcome to the forum, RadioBoy!

I will have a name change soon. By the way, welcome to the Philippines, Pope Francis!

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,647

hi RadioBoy,

**Welcome to the forum.**

For example, the miracle of digit 9. The product of digit nine in interaction with itself will always be nine (9 x 9 = 18 = 1+8 =9).

or a number that reduces to nine eg. 109739369 x 9 = 987654321 ....9+8+7+6+5+4+3+2+1= 45 ... 4+5 = 9.

So here's a challenge:

Why does this happen?

Why doesn't it happen for, say, 7?

What other numbers does it happen for?

Bob

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

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