Mathematics.Mathematical Jokes and Puzzles

Mathematics Forum

Author	Message / Information
bperrault Quote \| Reply \|	7up commercial posted on: 10/29/2003 2:19:18 PM OK - I assume someone else has seen this: http://digicc.com/fido/ And NO, I am not shilling for soft drinks. I just want the principle behind this math trick. Any help out there?
Soroban Quote \| Reply \| This message was updated on 10/31/2003 9:20:15 AM by Soroban	7up commercial replied on: 10/31/2003 9:07:03 AM Hello, bperrault! Given a number, say 5892, its "digital root" is found by adding its digits: 5 + 8 + 9 + 2 = 24 If the sum has more than one digit, add its digits: 2 + 4 = 6. The digit root of 5892 is 6. If we scramble the digits, the digital root is still 6. Subtracting the two numbers, the digit root of the difference will be 0 or 9. (There is a lengthy reason for this ...) When we omit a digit in the difference, it can be easily determined. For example: 5892 - 2598 = 3294 Note that the digital room of 3294 is 9. If we omit the "2" and enter "394", the digital root of 394 is 7. Since the digit root was originally 9, they know that a "2" was omitted.
glp Quote \| Reply \|	7up commercial replied on: 4/10/2006 9:48:02 PM My son would like to read the "lengthy reason." Can you give me directions to find it? Thank you glp
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