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originally posted by: ByteChanger
originally posted by: GBP/JPY
Please I beg of you someone explain it casting out nines to me.
Down demon, begone now I say! I cast thee back into the eternal pit of darkness from whence you came!
originally posted by: Lumenari
a reply to: Tucket
Something useless our mother taught us when we were learning our multiplication tables...
How can you tell if a number can be divided by 3 to a whole number?
Add the numbers up.
12 would be 1+2... which equals 3 so is divisible by 3. 12/3 =4.
123 would be 1+2+3... which equals 6 so is divisible by 3. 123/3 =41
12,345,678 would be 1+2+3+4+5+6+7+8... which =36... 3+6 =9, which is divisible by 3. 12,345,678/3 =4,115,226
123,456,789,233,412 would be 1+2+3+4+5+6+7+8+9+2+3+3+4+1+2... which is 60... 6+0 =6 so is divisible by 3.
123,456,789,233,412/3 =41,152,263,077,804
So you can figure out if any number is divisible by 3 by using simple addition in your head.
This was the secret of the Trinarians. Then, they ate Pi.
The Bible called it an "apple", but, whatever...
originally posted by: new_here
a reply to: Tucket
Posting in this thread to leave a trail so I can find my way back and learn more tricks!
I like math tricks, 'cause math can be tricky!!
originally posted by: DictionaryOfExcuses
a reply to: Tucket
I possess no special math prowess. However, sometime during my years I learned a quaint little arithmetic trick which I will present to you now.
Here goes:
1) Multiply any number by 9.
2) Obtain the digital root by adding each digit of the resulting product together. If this yields a sum comprised of two or more digits, repeat the process until you're left with a single digit.
3) It ALWAYS equals 9.
Examples:
A) 5×9=45; 4+5=9
B) 10×9=90; 9+0=9
C) 123,456,789×9=1,111,111,101; 1+1+1+1+1+1+1+1+1=9
D) 987,654,321×9=8,888,888,889; 8+8+8+8+8+8+8+8+8+9=81; 8+1=9
Try for yourself.