|
|
|
|
|
|
|
|
CTK Exchange
alexb
Charter Member
2767 posts |
Feb-15-11, 04:29 PM (EST) |
|
1. "RE: Digitla Roots"
In response to message #0
|
This is because any power of 10 modulo 9 equals 1, implying that the digital root of a number is simply the remainder of division of that number by 9. Let you have two numbers (9a + b) and (9c + d), b being the digital root of one, d of the other. Then (9a + b)(9c + d) + 9(ad + bc + 9ac) + bd = 9k + bd. It follows that the remainder of the division by 9 of the product equal the remainder of the division by 9 of the remainders. But the remainders are the digital roots. |
|
Alert | IP |
Printer-friendly page |
Reply |
Reply With Quote | Top |
|
|
You may be curious to have a look at the old CTK Exchange archive. Please do not post there.
Copyright © 1996-2018 Alexander Bogomolny
|
|