Any maths experts, do you know the answer to this question?
http://forums.dpreview.com/forums/read.asp?forum=1012&message=11469199

the answer is quite complex, so I'll break it down into simple chunks just in case you've never done degree level mathematics... right...

first off, you have 3 doors... you pick one... it's obvious the host will pick one of the ones that doesnt win to reveal to you...

so chances are you either picked a wrong one to start off, or you picked the winning one...

the next set of mathematics gets a bit complex...

basically, you pick whichever one you want :P the odds are 50/50, unlike what it would be in other situations its not 66/33 it IS 50/50 due to the fact the host will always remove a booby prize...

whats hard about that? :P pick a door and stick with it, thats what i'd do... saves looking a dick on TV and being undecisive

What if there is 100 doors,1 prize.You choose 1 (1chance in 100) 98 are discarded leaving your choice and the hosts.Your choice is99 /100 If you switch.

the point is, if there is only one item to win and the ones that are removed are always the ones you dont want then your odds are always the number thats left...

100 to 3 means you've a 3 in 1 chance of winning, whichever you end up picking, be it the one you chose originally or one of the other two

there is a 1 in 3 chance at the start. 1 is discarded (also a 1 in3 chance) so the one left now becomes a 2 in3 chance because yours is still 1 in 3.

It's obvious - you should switch. This is an old chestnut.

Originally posted by matsalleh
there is a 1 in 3 chance at the start. 1 is discarded (also a 1 in3 chance) so the one left now becomes a 2 in3 chance because yours is still 1 in 3.

No, as Xafier said after one door has been opened it becomes a 50/50 or 1 in 2 chance you have to count each choice individually.

Originally posted by Phanerothyme
It's obvious - you should switch. This is an old chestnut.

That's true it is an "old chestnut" but statistically you have as much chance sticking with your original choice. For example add into the equation that the host knows which is the winning one and that they invariably try to sway the choice of the contestant - are they trying to sway you towards the winning door or away from it? Some would say away and some would say towards it depends upon your point of view but in reality it is down to sheer luck!

Originally posted by matsalleh
1 is discarded (also a 1 in3 chance) This one's not a chance, it's a cert - and a dud. EVERY TIME.

This ALWAYS leaves your door and one other. But it's not your door yet - so you're choosing ONE from the remaining TWO.

The initial choice between 3 is a red herring.

If the show went 'Here's 3 doors. There's one dud. Choose one of the others.' We wouldn't be questioning the reasoning

The Host knows which is which,is he steering you to or away from the prize?
If you switch the odds become 67% in your favour, so if you stick 33% against.

Originally posted by matsalleh
The Host knows which is which,is he steering you to or away from the prize?
If you switch the odds become 67% in your favour, so if you stick 33% against.

No that's wrong this is a separate choice so the odds are 50/50 i.e. 50% for and 50% against forget the original choice that no longer comes into the equation at this point.

Originally posted by Phanerothyme
It's obvious - you should switch. This is an old chestnut.

This old in fact:

Previously, on a forum near you (http://www.sheffieldforum.co.uk/showthread.php?postid=11745#post11745)

Here you go check this out :-
http://www.grand-illusions.com/simulator/montysim.htm

Or Google Monty Hall

Originally posted by max
This old in fact:

Previously, on a forum near you (http://www.sheffieldforum.co.uk/showthread.php?postid=11745#post11745)

According to some sources over 100yrs in some guise or another.

No comments from the all but one person who got the right answer?
If you don't behave I'll put another one on !

Switch.

If you don't switch, you have a 1 in 3 chance of having the correct answer.

If you do switch, you have a 1 in 2 chance.

Following on from this ... if you do switch ... what is the % chance you will have the winning door !?

As already stated - it's an old well known puzzle and you should switch - gives you a 2/3 chance. Not obvious at first and takes a bit to get your head round it :)

I thought this thread was dead.If all you non believers and those who insist on sticking read some of the earlier posts you will find a link to a simulator where you can run as many goes as you like. It always comes out 66% to switch,try it 10 million times and then maybe some of you might realise that is not 50/50 as you insist.
Merry Christmas to you all.

Or just do it in front of yourself with 3 items representing the doors e.g. three glasses... Makes perfect sense then :)