The warlock police (brain teaser)

estebanrey · 22 Mar 2013 at 22:42

The warlock police burst through the doors and arrest two flatmates on suspicion of having magical powers. To prove it they are told a test will be carried out, they would both be placed in separate sound-proof rooms, each with a guy with a pack of cards in it.

The guy in each room will shuffle his deck and the suspects will pick one at random each, then they will be asked independently what colour the other person chose. If they are both correct then it proves they have psychic powers and thus they are warlocks and they are executed. This test will be run twenty times and if they both get each other's card on the same go even once it's off to the gallows.

The flatmates are then chucked in the back of a paddy wagon together and driven off to the station to be tested.

Once there they go into their respective rooms and go through all twenty tests and not once did they both get each other's card. So they are let go!

So, how did they do it?

Additional information...
* Once in the test the flatmates can't communicate in anyway, they don't know what the other person chose, only their own card.
* If picking colours at random, there should be a 99.7% chance of being convicted.
* They are normal people and not actually psychic.
* It is a standard deck of 52 cards (no jokers) and each player can only say red or black.

PLEASE PLACE THEORIES/SOLUTIONS IN SPOILERS PLEASE

dirtychinchilla · 22 Mar 2013 at 22:44

They determine which colour card it is and then say the other colour, so that they are wrong.

Judgeneo · 22 Mar 2013 at 22:45

You pick red, I pick black

P3N9U1N · 22 Mar 2013 at 22:46

They got lucky, picking random colours with .3% chance

estebanrey · 22 Mar 2013 at 22:47

dirtychinchilla said:
They determine which colour card it is and then say the other colour, so that they are wrong.

They don't know what the other person picked and must name that colour.

estebanrey · 22 Mar 2013 at 22:48

Judgeneo said:
You pick red, I pick black

That doesn't work.

If P1 always picks red and P2 always picks black then they will fail the test if P1 picks a black card and P2 picks a red card.

dirtychinchilla · 22 Mar 2013 at 22:48

estebanrey said:
They don't know what the other person picked and must name that colour.

If they can use psychic powers then they can see which card has been picked without getting into the other person's mind.

estebanrey · 22 Mar 2013 at 22:51

dirtychinchilla said:
If they can use psychic powers then they can see which card has been picked without getting into the other person's mind.

They're not actually warlocks. The warlock police aren't nice people.

Rich_L · 22 Mar 2013 at 22:52

The rooms may be soundproof but it has a big window in the wall so they can just see what the other one picks.

dirtychinchilla · 22 Mar 2013 at 22:55

estebanrey said:
They're not actually warlocks. The warlock police aren't nice people.

Well this was never stated.

P3N9U1N · 22 Mar 2013 at 22:56

I also assumed they were actually warlocks, one of my theories goes to pot.

Destination · 22 Mar 2013 at 22:56

They are psychic.
They know what the other picks.
The announce the wrong answer each round.

Its the old witch test, anyone who survives shouldn't.

P3N9U1N · 22 Mar 2013 at 22:57

Hikari Kisugi said:
They are psychic.
They know what the other picks.
The announce the wrong answer each round.

Its the old witch test, anyone who survives shouldn't.

But they aren't psychic...

estebanrey · 22 Mar 2013 at 22:59

Rich_L said:
The rooms may be soundproof but it has a big window in the wall so they can just see what the other one picks.

estebanrey said:
Additional information...
* Once in the test the flatmates can't communicate in anyway

Destination · 22 Mar 2013 at 22:59

P3N9U1N said:
But they aren't psychic...

Yes they are.
The just lied to he OP.

iamdjdz · 22 Mar 2013 at 23:11

In the van as they are together they agree that they will say alternate colours with one starting on red the other black.

Droolinggimp · 22 Mar 2013 at 23:15

estebanrey said:
, then they will be asked independently what colour the other person chose.

You didn't state if they was to chose from the deck of cards colour or not. If not then they can chose from thousands of colours.. one could say green the other lavender orange for instance.....

Edit

r in the van they agree one say red ad the other say black all the time.

estebanrey · 22 Mar 2013 at 23:20

Droolinggimp said:
You didn't state if they was to chose from the deck of cards colour or not. If not then they can chose from thousands of colours.. one could say green the other lavender orange for instance.....

Nice thinking but no, I've updated the rules.

Droolinggimp said:
Editr in the van they agree one say red ad the other say black all the time.

iamdjdz said:
In the van as they are together they agree that they will say alternate colours with one starting on red the other black.

Neither of those would work. Because when they do pick different colour cards they have a 50% chance of getting them both right.

But I can feel people starting to get there

Rich_L · 22 Mar 2013 at 23:30

Well I think worked out the answer but I'm trying to figure out how they arrived there assuming they weren't allowed any communication about the nature of the game etc

Person 1 always picks the same colour that they draw, Person 2 always picks the opposite

Trying to work out how they decide who is going to stick and who is going to flip

pepp77 · 22 Mar 2013 at 23:35

Rich_L said:
Well I think worked out the answer but I'm trying to figure out how they arrived there assuming they weren't allowed any communication about the nature of the game etc

Person 1 always picks the same colour that they draw, Person 2 always picks the opposite

Trying to work out how they decide who is going to stick and who is going to flip

Not sure that would work.