Since I was a kid, nobody wanted me in their super-exclusive clubs... the "House in the Tree Club"... the "Girls Only Club"... the "Whatever you are NOT Club"... but now that I am a skilled (and a bit nerdy) guy, time has come to take my revenge!
I've just discovered that not far from my house in New York City, there's a secret place where some guys seem to meet every week. I don't know what kind of club it is, but I definitely want to be a part of it!
Every night, each member knocks at the door of the Secret Club, and each time, a voice comes from inside, asking some strange questions...
At this very moment, someone is knocking on the door... ( - Let's listen to what they say... - )
"Who's knocking?" asks the voice.
"I am a member Sir, let me in!" answers the guy.
"If you're a member, tell me what are the results of these operations: 17 + 5? 24 + 3? 1 + 16?".
"Of course... 22... 27... 17!" is the guy's response.
"Very well! Come on in!".
(- Well, I guess it's not the MENSA Club... - I think...)
A second guy approaches the door, knocks at it, and again the same scene takes place:
"Prove that you're a member! Answer these: 38 - 37? 28 - 10? 14 + 4?"
"Ehm... 1... 18... and again 18!".
"Good boy! Come in and take a seat near the other guys!".
(- OK, it must be some sort of math-nerd association... but better than nothing!...)
One last guy knocks at the door, but this time the question they ask him is very very strange...
"Well, if you are really one of us, tell me... What's our special number... the one with the unique property we all know?..."
The third guy seems slightly surprised... keeps thinking for a while, and then shouts: "Ah ah!.. You're referring to 12! Are you?".
The voice from inside the house starts laughing "Ah ah! For sure you are one of us!", opens the door and lets the guy in...
(- Well... I am a bit disappointed... but I'll give it a try... I'm sure they'll let me in!-)
"Knock knock!... ehm... I'm a member! Let me in!"
"Are you sure? If so, tell me... What's the result of 11 + 1? 10 + 17? 21 + 3?"
"...Ehm... 12... 27..." I start answering...
"OK... and what about the last one?" says the voice
"24!!" I shout... just a second before the guy from inside starts to yell:
"You liar! Go away and never come back to this respectful club!!"
At the end of this shocking experience, I still have a question in my mind:
"WHAT KIND OF CLUB WAS IT THAT I WAS TRYING TO ENTER?"
The club is a real club. Many clubs like this one exist in real life. Probably, many members of the Puzzling Community are members of such a club in real life. Of course, the secrecy about the club is purely "fictional" and for the purpose of the puzzle.
One of my guesses about the club's members was completely wrong: they ARE NOT "math nerds", and you don't need particular math skills to solve the calculations asked by the man at the door. Anyway, not everybody could answer those questions like the members did.
Pay attention to the tags: no calculation-puzzle is present...
It appears that the right answer to the last question of the man at the door should have been "23" instead of "24"...
In my last edit I added a location for the story. Though it is not strictly necessary, it could be important to solve the puzzle.
Twelve is "special" for club's members, because is the only number with a specific characteristic; anyway it's not so obvious, that's why the member who was asked about it had to think a while before answering...