This is a puzzle of a game where I know the solution, but not how it is derived. So the correct answer goes to whoever can also explain the solution.

Find the correct code:

This is written on top of a closed door:


And this is a number on the closed door: 13

On the floor the following table can be found:

A | + | 2
- | 3 | -
8 | + | D

You have to find the correct 4 digit code.

Since nobody found the solution after a week, I'm now adding a part of the correct answer as hint. If this doesn't help, I'll add the complete solution in another week.


The middle part of the code contains the 13: so A13D
A and D are replaced by single digits. But which?


closed as too broad by Rohcana, Deusovi, Rand al'Thor, The random guy, CodeNewbie Aug 25 '15 at 9:33

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Is the door locked? If it is closed, how can we read what is written on top of it? $\endgroup$ – chasly from UK Aug 16 '15 at 11:57
  • $\begingroup$ @chaslyfromUK It's written above the door $\endgroup$ – Marwie Aug 16 '15 at 12:51
  • $\begingroup$ You mean on the door-frame or on the wall above the door? Is it significant precisely where it is written? $\endgroup$ – chasly from UK Aug 16 '15 at 12:57
  • $\begingroup$ @chaslyfromUK on the wall $\endgroup$ – Marwie Aug 16 '15 at 12:59
  • 2
    $\begingroup$ Is there any significance to the fact that $2^3=8$? $\endgroup$ – tfitzger Aug 17 '15 at 13:05

So my theory is it works for reading across and up and down.

So two equations with 2 unknowns:

$A+2-3-8+D=13$ and $A-8+3+2-D=13$

Simplfies to $A+D=22$ and $A-D=16$

Which rather simply goes to $A=19, D=3$

As we are looking for a 4-digit code 1903 works using 19 and 03 as the numbers. This has extra appeal as (recent) year numbers are popular 4-digit passwords.

Alternatively we are given A..D. So I propose A19D as the code as A..D has room for two more digits. I am not convinced on the code part but I think the arithmetic part is valid.

  • $\begingroup$ Could it be 1903? $\endgroup$ – Gordon K Aug 16 '15 at 20:16
  • $\begingroup$ Alternatively the .. Could mean that the code should be the numbers represented by B and C. However if the numbers A to D are spaced uniformly on the number line, B and C are not integers. $\endgroup$ – Gordon K Aug 16 '15 at 20:21
  • $\begingroup$ @GordonK I like 1903, I was pondering it but I didn't put it into my head as 1903, I thought of it as 19 03. Years starting with 19 are rather common pin codes so that lines up nicely. I do like that better than A19D... Might put that into the answer, I just wish you didnt have to add a seemingly arbitrary number, though I suppose omitting the 3 is just as odd... As 4-digit tends to refer to numbers, I will go with 1903, but A19D is perfectly valid hex so that is somewhat interesting. $\endgroup$ – Going hamateur Aug 16 '15 at 22:33
  • $\begingroup$ The code is digits only. No Hex. Unfortunately 1903 isn't the right answer. $\endgroup$ – Marwie Aug 17 '15 at 4:30
  • $\begingroup$ If A..D refers to the diagonal line in the diagram running from A to D then the answer could be 19 3 3 $\endgroup$ – Gordon K Aug 17 '15 at 16:08

Is the answer:

7133 ?

Based on the hint that:

A and D are both one digit numbers, and the code is A13D

I tried using a variation on the approach that Going Hamateur used...

I set:
A+2-3-8+D = A-8+3+2-D
A-9+D = A-3-D
D = 3
When I substituted 3 for D, I found A-6=A-6

I then applied Moonbutt74's observation that:

The Diagonal 2+3+8 = 13.I then solved A+3+D=13
D=3, so A=7

Therefore, I believe the code is:


  • 2
    $\begingroup$ I would be so happy just to see the correct answer because this really is making me nuts. $\endgroup$ – moonbutt74 Aug 24 '15 at 1:25
  • $\begingroup$ @Marwie Is this the code? $\endgroup$ – Matthew0898 Aug 24 '15 at 19:58

A is number 11, D is number 5.

The first row A+2 = 11+2 = 13, what is written on the door.

The same is 8+D = 8+5 = 13.

For columns A-8 = 11-8 = 3, the number in the centre of table.

The same is D-2 = 5-2 =3.

So you have to type AD = 1105

  • $\begingroup$ Okay upvote for the new angle, but it's the adding of the zero, that's still throwing me. $\endgroup$ – moonbutt74 Aug 20 '15 at 23:45
  • 1
    $\begingroup$ @moonbutt74 I think the 0 comes because there is "A..D". Points mean that there are 4 numbers, so 05 for D $\endgroup$ – Voitcus Aug 21 '15 at 8:38

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