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casting out 9s

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3 items are filed under this topic.
The cube root of 729 2014-11-12
From Alexis:
What would be the square root of 729 to the third power and could you explain how to get the answer?
Answered by Penny Nom.
What's it called? 2004-04-22
From Gerry:

I'm a father and a grandfather and have come up with a game for my offspring to play while we're on the road. When we see a license plate, the object is to be the first one to add all the numbers on it, and come up with THE one digit number that sums them up.

For example: ABC-787 = 7+8+7 = 22 = 2+2 = 4

Another example is 2932 = 2+9+3+2 = 16 = 1+6 = 7

Up 'til now, I've called it just plain "Numerology", but I'm sure that there's a math term for what we're doing, and I'd sure appreciate it if you could tell me what it is!

Answered by Chris Fisher and Penny Nom.
Divisibility by 9 2000-10-24
From Kelera:
If the sum of the digits of a number is divisible by 9, then the number itself it divisible by 9. Why is that? How do you explain this?
Answered by Penny Nom.



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