Construct 4-Digit Number: Greatest to Smallest

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Discussion Overview

The discussion revolves around constructing a four-digit number using distinct digits, specifically focusing on finding the greatest and smallest numbers that can be formed from those digits. Participants explore the conditions under which the difference between these two numbers consists of the same four digits originally chosen.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant poses the problem of constructing the greatest and smallest four-digit numbers from four distinct digits and questions whether the difference between these numbers can consist of the same digits.
  • Another participant suggests that the thread may not belong in the forum, indicating a potential disagreement about the appropriateness of the topic.
  • A participant reiterates the original problem, providing a structured approach to comparing the digits and constructing the numbers.
  • One participant claims that the digits 6, 1, 7, and 4 yield a specific result known as the Kaprekar Constant (6174), noting its significance in the context of the problem.
  • A later reply mentions that starting with any four-digit number and applying the Kaprekar Algorithm leads to either 0 or the Kaprekar Constant, suggesting a broader application of the concept.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of the problem to the forum. While some engage with the mathematical exploration, others question the appropriateness of the topic, indicating a lack of consensus on its placement.

Contextual Notes

The discussion includes assumptions about the distinctness of digits and the process of comparing numbers, but does not resolve the broader implications of the Kaprekar Constant or the algorithm's iterations.

Who May Find This Useful

Readers interested in number theory, mathematical puzzles, or the properties of the Kaprekar Constant may find this discussion relevant.

whoelsebutme
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4 digit number...

Consider four distinct digits.

Construct the greatest four digit number out of those digits.

Now construct the smallest number, again from those four digits.

If the difference of the two numbers consists of the same four digits as chosen originally, can you find the four digits?

:confused: :confused:
 
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This doesn't belong in this forum. Try general maths.
 
whoelsebutme said:
Consider four distinct digits.

Construct the greatest four digit number out of those digits.

Now construct the smallest number, again from those four digits.

If the difference of the two numbers consists of the same four digits as chosen originally, can you find the four digits?

:confused: :confused:
Say, you have 4 digits, namely: a1, a2, a3, and a4, and that: a1 > a2 > a3 > a4.
To compare 2 4-digit numbers, say abcd, adn efgh, one must first compare the thousands right? If a > e, then abcd > efgh.
If a = e, we continue to compare the hundreds, then... blah blah blah.
Can you get this?
---------------
Now if you want to construct the greatest number from these digits, how can you do that?
Can you go from here? :)
 
the answer is 6, 1, 7, and 4

*just for knowledge, the number 6174(the answer) is called the Kaprekar Constant. If you do with this number, exactly as written above, then you always get the number back...
 
In fact, if you start with any 4-digit number and go through a bunch of iterations (of the Kaprekar Algorithm, each step involving the process described in the OP), you end up with either 0, or the number above.
 

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