Help Needed: 4-Digit Combination for Non-Profit Safe

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Discussion Overview

The discussion revolves around finding a 4-digit combination for a safe donated to Habitat for Humanity. Participants explore the potential combinations based on four specific numbers (2, 5, 8, 7) that appear worn on the keypad. The conversation includes technical reasoning about combination possibilities and the implications of worn keys.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant suggests that if all four keys are equally worn, there are 10,000 combinations to try, assuming a 4-digit combination.
  • Another participant outlines a method for generating combinations starting with one of the digits and permuting the remaining digits, indicating that if the combination is indeed four digits, the number of combinations is manageable.
  • Some participants express skepticism about the number of possible combinations, suggesting it is fewer than initially thought.
  • One participant humorously notes the similarity of the question to homework problems, indicating a potential concern about the nature of the inquiry.
  • A later reply provides a hypothetical scenario using different worn keys to illustrate how to calculate the number of possible sequences based on permutations.

Areas of Agreement / Disagreement

Participants express differing views on the total number of combinations possible, with some suggesting it could be as high as 10,000 while others argue it is significantly lower. The discussion remains unresolved regarding the exact number of combinations.

Contextual Notes

Participants have not reached a consensus on the assumptions regarding the condition of the keys or the exact nature of the combination, which affects the calculations presented.

PAHH
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Hello all:
This may be the only question I ever ask here, so pardon if I posted in wrong forum.

I work for Habitat for Humanity, a non-profit 501(c) (3) org. A local business donated an open floor safe without a combination. We could really use this safe in our office. The manufacturer no longer has the master combination and want over $500 to come out to fix. We can't afford that, but from looking at the keypad, there are 4 numbers that look dirty and well used. Those numbers are: 2587

Can anyone provide me a list of all the number combinations possible for those four numbers?
 
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Does one of the keys look much more worn/dirty than the other three? If they are all equally worn, maybe you are lucky, and there are only 10,000 combinations to try.
 
If you start with 2, next digit can be 5, 7 or 8:

25
27
28

In each case there are only two digits left and they can be in two different orders. Repeat for 5 (followed by 2, 7, 8), 7 (followed by 2, 5 8) and 8 (you should see the pattern now).

That is, assuming combination is four digits. If it is longer it will be more complicated.
 
turbo-1 said:
Does one of the keys look much more worn/dirty than the other three? If they are all equally worn, maybe you are lucky, and there are only 10,000 combinations to try.

Thanks for response. As I said: "but from looking at the keypad, there are 4 numbers that look dirty and well used. Those numbers are: 2587."


Much appreciated
 
Surprising, how similar to some homeworks this question is...
 
turbo-1 said:
Does one of the keys look much more worn/dirty than the other three? If they are all equally worn, maybe you are lucky, and there are only 10,000 combinations to try.
Oops! :redface: Silly me.
 
Not that many possible combos when there are only 4 keys in a 4-number combo. WAY not.
 
Borek said:
Surprising, how similar to some homeworks this question is...

Thanks Borek, but no one has "carded" me in over a decade. I also have gray hair for all that's worth, but if you are afraid of providing an answer, that's fine. Actually, my concern was not being perceived as a snot nosed child, but as a burgler. I assure you, I am as I stated.
 
Let's pretend the worn keys are "1", "2", "3", and "4" and that they are equally worn and dirty. Best-case means that you have a 4-digit combination. If the combo starts with "1", you can have:
1234
1243
1324
1342
1423
1432

That's 6 possible sequences. If you substitute "2", "3" and "4" for the "1" and write down those combinations, it's a pretty short list.
 

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