Logic puzzles 5 - Cognitive illusions

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A slight varient. I've been reading a rather good book about cognitive illusions and their use in society. Cognitive illusion being like an optical illusions but its the brain which gets it wrong.

I've no doubt you unwholesomely clever bunch will get them straight away but i thought they were quite clever.

1.
I have three boxes. With your back turned i put £20 in one of them.

I offer you a free choice of boxes. You choose one leaving me with two.

I discard one of my boxes which i know to be empty so now i have a box and you have a box. One of us has the box containing £20, i know which one but you don't.

I offer you the oppertunity to swap boxes with me or to stick with your present choice.

Should you A: swap or B: stick or C: does it make no difference.

More to follow...

 

Slight variant, eh Robert!

Isn't this one of those "unless you began using this particular neuron in you brain at the age of seven months, and could simultaneously pick a combination lock with your left hand and solve a Rubiks Cube with your toes by your second birthday, you'll never have any chance of answering this question" type of question?

Thanks for the frustration :bang:

 

It seems simple enough does'nt it?

Love to make you think.

To switch or not to switch. Or does it make a difference?

Robert

 

have you been reading the Derren Brown book by any chance?

 

Its VERY good init.:drinks

Learned to do the memorizing deck of cards thing successfully as well.

Robert

 

does it make a difference? Do you get to keep the money? Can you rattle the box? Do you know which it is because you remember or you can rattle it?
IOna:bang:

 

can I play can I play can i can I ooh ooh
SWAPPPPPPP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ITS STILL 66.6% CHANCE SO SWAP

 

Thats a small cigar and an attaboy for mark!:drinks

You should swap the boxes.

This is a tricky one because when there are two choices and you get a free choice your brain tends to consider it as a 50 50 because it struggles to process what went before.

Consider it this. Initially there is a 2/3 chance you'll pick the wrong box. If you do i have to remove the OTHER wrong box meaning the remaining one is the one with the money. Therefore 2/3rds of the time if you swap you'll get the dosh.

Other possibility is that 1/3 of the time you pick the RIGHT box. In which case obviously you should stick.

So the odds are much better if you swap.

Looked at another way lets say i have 1 000 000 boxes. You pick one your odds ain't too clever. But if i then removed all but one of the remaining and offered you a choice you'd be a mug not to take the one i left you!

Well done mark and thankyou monkey rob for not spoiling it for everyone else!

Robert

 

Robert, please, can I have more!!!!!!!!!!!!!!!! after a week with a gouty foot keeping me home bound I'm desperate ........................... for logic puzzles and the like, cheers, mark c