# Pairs of numbers

You wake up in a cell after a party. You just remember the beginning of the night: you talked to your friends, you drank some alcohol, and then you blacked out.
You stand up and look around you: you are in a small empty room with no window and a door locked with a numeric keypad.

You approach the keypad and notice a piece of paper:

You'd better not try to steal my spaghetti recipe again!
I'll let you out if you can solve this puzzle:

{22,11}
{49,83}
{76,56}
{157,344}

are all acceptable numbers, but

{11,22}
{72,47}
{31,70}
{512,114}

aren't.

If you find the key, you can live. (And if you fail, my pet elephant will make sure you wish you weren't alive...).

## Question:

What is the key to the puzzle?

## Hint :

The key is 2-char long

(Note: This isn't a lateral-thinking question, so there's no need for ridiculous answers like "I punch through the wall".)

• I edited it to fix the grammar and spelling. Wasn't sure what you meant by the "key to the puzzle" (I'm guessing the pattern has some number that stands out), and I assumed a "digicode" was a keypad with numbers on it. – Deusovi Jul 28 '15 at 10:29
• @Deusovi: Great clean up. I was itching to clean it up too, but saw that it was too much work, so I gave up. – CodeNewbie Jul 28 '15 at 10:34
• So just to confirm, the key is a single number input on the keypad? – Set Big O Jul 28 '15 at 12:39
• So is I FALCONPUNCH through a wall still valid? – Going hamateur Jul 28 '15 at 12:55
• @Geobits exactly – The random guy Jul 28 '15 at 12:56

I'd do some quick addition and type

42

because each number on the left

turns into 4 if you repeatedly add digits until you get a single digit (49 -> 4+9=13 -> 1+3=4)

and each on the right

results in 2 (83 -> 8+3=11 -> 1+1=2)

In the invalid pairs, at least one of them is wrong.

Also, you know, it's the answer, assuming you know the question.

• Well play, well play :) – The random guy Jul 28 '15 at 13:42
• For all that may need a hint to the answer :) 42 – Marek Oleszczuk Jul 28 '15 at 13:52
• That's a pretty blatant hint :P – Set Big O Jul 28 '15 at 14:08
• This makes me sad, I was adding digits and I was like of so the left needs to sum to more than the right. But that didn't hold. AAND I just shoulda paid some attention to the actual sums... (and then repeated). but gj. – Going hamateur Jul 28 '15 at 14:49
• @Goinghamateur To be fair, I should credit qwertylpc somehow. His deleted answer led me to the idea. I just don't know how to appropriately credit deleted answers, since many users can't see it. Well, besides this roundabout way, I guess. – Set Big O Jul 28 '15 at 14:52