Calling math nerds. Help me pick a lock!

[Rabblevox]

I'm doing some fall cleaning, and ran across a cable/tumbler lock that I hadn't used for years. Combo long forgotten, but I remember clearly that it had 1,2 together in the sequence.

It's 4 tumblers, running from 1-6 (no 0's)

So the combo could be:
1,2,A,B
A,1,2,B
A,B,1,2

(with both A and B being positive numbers 1-6)

Can anyone help me suss out how many possibles there are? And if there's a more elegant way to go about picking it than repetitive brute force?

[Happyhippychick]

1. Major math nerd here. The answer:

A shitload

:)

Sounds like a project for a neighborhood kid!

[PoliticAverse]

2. There are 36 (6 for A x 6 for B) possible combinations for each of the three lines...

for a total of 36 * 3 = 108 different possibilities - 1 (for the identical 1212 possibilities in line 1 and 3 ) = 107 different possibilities

[Rabblevox]

5. 107 actually sounds do-able. It helps that I am easily amused, and currently unemployed. /nt

[napoleon_in_rags]

8. Here's the general math for when these things come up:

http://www.mathsisfun.com/combinatorics/combinations-permutations.html

What you have here is 3 instances of permutation with repetition. You identified n=6 and r=2 for each one, 36+36+36

[RUMMYisFROSTED]

3. Bolt cutters.

:think:

[PoliticAverse]

4. It is sometimes possible to figure out the combination for such locks...

by putting tension of the cable while turning the dials so that you can feel where the notches are
or by inserting a thin wire in to find the notch locations. Youtube/google can help you there.

[Rabblevox]

6. I'll check. Thanks!

[saras]

9. Sometimes = almost always, except rare expensive locks

there are 107 possibilities

best case: you pull on it, and one wheel is conspicuously harder to turn, and has one position it snaps into. leave it there. now, find the next hard-to-turn wheel, and turn it until it clicks. two more and you're done.

worst case: you have to set the last dial one number at a time, it has a fake click on every position, and you have to let go and pull again each time.

keep it laying around and you'll get it in a handful of 5 minute sessions.

[zbdent]

7. contact the manufacturer with the serial number of the lock?

I'm not sure if that would work ... I doubt it, but hey, it's an idea ...

I know it was a "movie", but "Mad Money" had a similar option ...

[customerserviceguy]

10. Reminds me of a briefcase I bought about twenty years ago

It was 70% off, and that was off of a discounted price. The catch was that it was locked, and no one had the combination. That's why it survived to the 70% off stage of that store-closing sale.

It took me only an hour to pop the thing open. I still have it.

[LiberalFighter]

11. 1,2,3,4 ??

[krispos42]

14. Hmph, I have the same combination on my luggage n/t

[Rabblevox]

12. Ka-Ching! 3,1,2,5 (guess it's a good thing it's not currently locking anything...

ty to all, I ended up "brute-forcing" it, took the better part of an afternoon, but feels oddly satisfying.

[GKirk]

13. If you didn't recall any of the numbers

it would have been 6x6x6x6=1296 possibilities
where if it had been a 0-9 choice on the 4 tumblers it would have been
10x10x10x10=10,000 choices that one is easy to 'see' because you can set the tumblers to all 9s
and see the number 9,999 (the ten thousandth combo is 0000)