James Magan
New member
- Joined
- Nov 27, 2013
- Messages
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M
I started a string a while ago by asking some questions about the number 153.
I will first recap on a couple of observations made there, then ask a question to which I would be very happy to have the answer – or perhaps several answers.
So to recap:
a) 153 has an unsual property because if you sum the cube of its digits 13 (1) + 53 (125) + 33 (27), you arrive back at the original number, 153. The only other numbers that have this property are 370, 371 and 407 (and 1).
b) 153 is unique inasmuch as not only does it revert to itself if you sum the cube of its digits, but every number that is divisible by three in the entire numerical system is reducible to 153 if you sum the cube of its digits, then repeat the process on the product, and keep repeating it ... eventually you will arrive at the irreducible 153. The example that I gave was the number 3 itself, but it works on any multiple of 3. Here is 3 being “reduced” to 153:
33 = 27;
23 (8) + 73 (343) = 351;
33 (27) + 53 (125) + 13 (1) = 153.
Now here is my question. I discovered this information from various sources on the internet, and it was provided by people who were trained mathematicians: but what sort of maths is it? I cannot even formulate the question I am trying to ask very clearly, but what I mean is this: 33 = 27 is alright – even I understand that because it is simple arithmetic ... but what sort of a process is it when you take the result and instead of calling it 27, you simply call it a 2 and a 7?
I would understand it still to be arithemtic if you decided to treat 27 as a 20 and a 7 ... and if you added 203 and 73 together you would have 8343, or if you simply cubed 27 you would have 19683.
But in the process that I have been describing the base 10 system is collapsed into just a sequence of digits between 1 and 9, and irrespective of their place in the sequence, the digits are treated as being of equal “dignity” with one another. E.g. if the number 5 is in the penultimate place in the sequence, it is treated just as a 5 and not as 50. All the trailing zeroes disappear.
Is this valid mathematics? (Is there such a thing as valid and invalid mathematics?) What are the principles that it is based on? Or is this process of reducing any multiple of 3 to 153 simply a “conjuring trick”? I expect that a lot of conjuring is based on mathematics, but it seems to me that this process is at least in some way “serious maths”, because there must be some solid underlying numerical principle that produces this very consistent effect.
I guess that having a clear understanding (which I don’t) of the base 10 numbering system and number-base systems in general might help to clarify the answer for me. I also suspect that the relationship between 3 and 153 probably has something to do with a property of the number 3 which I have just discovered for myself with some amazement, namely that when you add the digits of any multiple of 3 together, the result is always divisible by 3 (so for example, 27 is 2+7 = 9; 99 is 9+9 = 18; 111 is 1+1+1 = 3, etc.) Therefore if you start the process described above with any multiple of 3, each new product in the process will also be divisible by 3 (because if the sum of the digits of a number is divisible by 3, so is the sum of its cubed digits) ... until things eventually boil down to 153. [It seems that 9 also has the same property as 3 if you sum the digits of any of its multiples (e.g. 63 is 6+3 = 9; 108 is 1+8 = 9; etc.), but none of the other numbers in the decimal system (except 1 of course) share this property.]
It has taken me a while to pose the question, but by exposing the extent of my ignorance I hope it will make it easier for the experts kindly to tailor their answer(s) in such a way that I might be able to understand it (/them)!
Any suggestions for further reading specific to this question would also be gratefully received. Many thanks.
M
I started a string a while ago by asking some questions about the number 153.
I will first recap on a couple of observations made there, then ask a question to which I would be very happy to have the answer – or perhaps several answers.
So to recap:
a) 153 has an unsual property because if you sum the cube of its digits 13 (1) + 53 (125) + 33 (27), you arrive back at the original number, 153. The only other numbers that have this property are 370, 371 and 407 (and 1).
b) 153 is unique inasmuch as not only does it revert to itself if you sum the cube of its digits, but every number that is divisible by three in the entire numerical system is reducible to 153 if you sum the cube of its digits, then repeat the process on the product, and keep repeating it ... eventually you will arrive at the irreducible 153. The example that I gave was the number 3 itself, but it works on any multiple of 3. Here is 3 being “reduced” to 153:
33 = 27;
23 (8) + 73 (343) = 351;
33 (27) + 53 (125) + 13 (1) = 153.
Now here is my question. I discovered this information from various sources on the internet, and it was provided by people who were trained mathematicians: but what sort of maths is it? I cannot even formulate the question I am trying to ask very clearly, but what I mean is this: 33 = 27 is alright – even I understand that because it is simple arithmetic ... but what sort of a process is it when you take the result and instead of calling it 27, you simply call it a 2 and a 7?
I would understand it still to be arithemtic if you decided to treat 27 as a 20 and a 7 ... and if you added 203 and 73 together you would have 8343, or if you simply cubed 27 you would have 19683.
But in the process that I have been describing the base 10 system is collapsed into just a sequence of digits between 1 and 9, and irrespective of their place in the sequence, the digits are treated as being of equal “dignity” with one another. E.g. if the number 5 is in the penultimate place in the sequence, it is treated just as a 5 and not as 50. All the trailing zeroes disappear.
Is this valid mathematics? (Is there such a thing as valid and invalid mathematics?) What are the principles that it is based on? Or is this process of reducing any multiple of 3 to 153 simply a “conjuring trick”? I expect that a lot of conjuring is based on mathematics, but it seems to me that this process is at least in some way “serious maths”, because there must be some solid underlying numerical principle that produces this very consistent effect.
I guess that having a clear understanding (which I don’t) of the base 10 numbering system and number-base systems in general might help to clarify the answer for me. I also suspect that the relationship between 3 and 153 probably has something to do with a property of the number 3 which I have just discovered for myself with some amazement, namely that when you add the digits of any multiple of 3 together, the result is always divisible by 3 (so for example, 27 is 2+7 = 9; 99 is 9+9 = 18; 111 is 1+1+1 = 3, etc.) Therefore if you start the process described above with any multiple of 3, each new product in the process will also be divisible by 3 (because if the sum of the digits of a number is divisible by 3, so is the sum of its cubed digits) ... until things eventually boil down to 153. [It seems that 9 also has the same property as 3 if you sum the digits of any of its multiples (e.g. 63 is 6+3 = 9; 108 is 1+8 = 9; etc.), but none of the other numbers in the decimal system (except 1 of course) share this property.]
It has taken me a while to pose the question, but by exposing the extent of my ignorance I hope it will make it easier for the experts kindly to tailor their answer(s) in such a way that I might be able to understand it (/them)!
Any suggestions for further reading specific to this question would also be gratefully received. Many thanks.