I wrote down the worked example and now I get it: 1) You have 100 doors to choose from - you choose number 69 - your chance of being correct is 1/100 2) The quizmaster now proceeds to open doors 1-68 and doors 70-99. He leaves door 69 (your choice) and door 100 (the quizmaster's "choice") closed 3) The chance of you having picked the correct door with your first choice is 1 in 100 - so 99 times out of 100 you would have been wrong with that original choice. Therefore 99 time out of 100 the quizmaster's "choice" (i.e. the other door he chooses to leave closed) will have the car behind it. So you should definitely change Phew my brain hurts now - time for lunch.
I think that's a good way of looking at it Zenyatta. Another one in a book published about 10 years ago was the chance of having 2 people with the same birthday (day and month only) from a football match (2X 11 players + 1 referee). It was also done on television a while later. So what's the chance.
I once "grossed out" a few of my fellow whippet owners on a caravaning holiday a few years ago. I'd been complaining I had nothing in the fridge for dinner, then I came out appearing to eat dog food out of a Pedigree Chum tin. In fact it was Tesco's steak and onion pie mix and I'd swapped the label Talking of Pedigree Petfoofds - did you know they were going bust? Then they called in the retrievers
Well RR there's a 365 in it. The usual view from us laymen is that the chance must be say 22 in 365, and that is true for person A. But for B the chance is 21 in 365. So if you go on adding each individuals chance 22+ 21 + 20 etc then the chance of two being the same is actually 253 in 365, nearly 66%. Try it. Everyone thinks you're an idiot when you say it but when you try it then out pops two people with the same birthday, or at least 2/3 of the time it happens, they are confused. This appeared in the book Fermat's Last Theorem about 12 years ago. I was unhappy with the explanation in the book because it said that it was because there are 253 couples (or doubles to us racing men) in 23 people. And there is, but what about 3 people having the same birthday? With the book's explanation there are 3542 trebles, does that make 3 a certainty? In fact 3 is obviously less likely, because for A the chance or probability is 22/365 times 21/365, which is a whole lot smaller number. Then for B it's a whole lot smaller still 21/365 X 20/365 and so on. But they showed the exercise on the box about 5 years ago for 2 people and randomly asking people in the street got to 19 people before they found 2 the same. Doesn't seem right but it is.
OK, let's change the theme. Here's two questions from the sixties- from an entrance exam to the CIA. 1.A man lives in a 23 storey block of flats. Every morning he goes into the lift- on his floor- and gets out at the ground floor; walks out of the building and catches the bus to work. In the evening, a friend drives him home and he gets in the lift to go back to his flat. However, he gets out at the 10th floor and walks up the remaining 13 floors to his flat. Why does he do this? 2. A man is walking in the desert when he comes across a cylindrical 20 foot high steel tower- fully enclosed all round and the only means of access is a large steel door. The door is open. He notices that there is a large flatbed lorry parked outside the tower, but there is no driver nor anything on the flatbed save a large, thick tarpaulin and security ropes. He walks into the tower. The inside walls of the tower are totally smooth with no projections or fixings. There is nothing on the floor. He looks up and sees a man hanging by the neck from a three foot rope attached to a steel hook in the ceiling of the tower. How did this happen? Clues..The CIA expect the most logical and probable solution. Entrants must be able to analyse the information and discard what is irrelevant.
Tam - in the first question the lift only goes to the 10th floor. We are told "Every morning he goes into the lift and gets out at the ground floor" - we assume he gets in at the 23rd floor, but the later statement "he gets out at the 10th floor and walks up the remaining 13 floors to his flat" infers that the lift only goes to the 10th floor - there is no logical reason for him to get out at the 10th EVERY day unless the lift goes no further. So each morning he walks down the stairs to the 10th floor and gets the lift from there.
Oddy, you have to make the probable and logical assumptions- but I will amend the question to help. Good morning, by the way!
He's a stupid midget - he should have a stick or ruler or some such in his pocket to push the 23 button with
Oddy- I love your humour (sick, like mine!) For that, I'll give you a clue (of sorts) to the second question. If you've ever seen the film, Three Days Of The Condor (Robert Redford), Redford works for the CIA and is asked how a man died when he wasn't poisoned or stabbed, and the only sign of any injury was a small hole in his chest (about 1/3 inch diameter) . There were no bullets in his body. If you solve this one, you'll solve my poser.
Haven't seen the Redford movie but my first thoughts were that the cylinder held a block of ice which the guy stood on the fasten the rope to the hook, then waited for it to melt ...... absurd, but possible!
Reebok, spot on! well done! The lorry transported blocks of ice which the man climbed up to hang himself. In the Redford movie, the man was killed with an ice bullet which melted inside his body.
Here's an old one... You are out walking to go to a certain village -and come to a fork in the road. Just before you come to the fork, you meet two brothers who live locally and know where the village is. One always tells the truth and the other always tells lies- but you don't know which is which. You are allowed to ask one question only- to ensure that you take the correct fork to your destination. What is the question you must ask?
