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Post by jean on Dec 14, 2010 9:52:54 GMT
This was posted on the Science proboard. It is a rude and unpleasant place and I don't advise going there, so I repost the problem here. There must be a simple answer, but it's driving me mad.
Three people go out for a meal. The bill comes and it is £30, so they each put in £10.
The waiter comes back a little embarrassed and says he'd make a mistake and the bill should have been £25. He gives them back £5.
They decide that because of the waiter's honesty, they would take back £1 each and leave the remaining £2 as a tip.
In the taxi on the way home, one of the diners decides to do the sums. He knows they each paid £9, making a total of £27. He knows they left a £2 tip, making a total of £29. He is mystified as to where the other pound went.
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Post by trubble on Dec 14, 2010 10:15:29 GMT
I know the answer. It's an old one but a good one.
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Post by rjpageuk on Dec 14, 2010 10:24:19 GMT
This is a well known logic problem (incidentally link me to the science board sounds fun) which messes with your head . The problem comes from approaching the problem from the wrong end and so it ends up confusing. Actually they paid £27 for the meal not £29 (£25 plus £2 tip). Look at it from the waiter point of view - he received £30, then gave back £5 and got to keep £2, so £27 was paid for the meal. This is then £9 each. There is no missing pound. If you want to work out where the £30 is, £27 of it went on the meal and the other £3 went back to the individuals.
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Post by rjpageuk on Dec 14, 2010 10:24:54 GMT
I know the answer. It's an old one but a good one. Telling someone who has a problem driving them mad that you know the answer but then refuse to say is very cruel!
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Post by trubble on Dec 14, 2010 10:30:03 GMT
I wanted to give the rest of the stubbers a chance to go mad. I am a giver.
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Post by trubble on Dec 14, 2010 10:34:54 GMT
I'd say it as:
It's a trick question, literally, because this part is a bit of a lie:
He knows they each paid £9, making a total of £27. He knows they left a £2 tip, making a total of £29. He is mystified as to where the other pound went.
The £2 tip has already been included in the £9 (and £27) already paid.
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Post by trubble on Dec 14, 2010 10:36:34 GMT
In fact, it is a bogus question.
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Post by everso on Dec 14, 2010 11:43:35 GMT
Well, I can't do the math. Frankly, I wouldn't have given the waiter a tip for being honest. It is expected that your waiter should be honest. This is actually a moral maze question.
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Post by jean on Dec 14, 2010 13:13:55 GMT
he £2 tip has already been included in the £9 (and £27) already paid. I think I've got it, or rather I've got an explanation I can understand. We are misled by the neatness of the original round figure £30, which would have seen them each paying £10, and the way the returned £5 can be divided (neatly) into £3, £2 and £1. I can see it most clearly if I say that instead of the £10 they'd each have paid for the meal at the original price, they now pay roughly £8.33; and then when the £2 tip is divided up between them, they each pay about 67p, giving a total of £9 each. The £3 should appear nowhere in the calculation of money paid out. It goes sraight into their pockets. Nobody on the Science board is condescending to answer because they are all too busy rubbishing each other's qualifications or pretensions to understand anything.
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Post by everso on Dec 14, 2010 13:56:48 GMT
he £2 tip has already been included in the £9 (and £27) already paid. I think I've got it, or rather I've got an explanation I can understand. We are misled by the neatness of the original round figure £30, which would have seen them each paying £10, and the way the returned £5 can be divided (neatly) into £3, £2 and £1. I can see it most clearly if I say that instead of the £10 they'd each have paid for the meal at the original price, they now pay roughly £8.33; and then when the £2 tip is divided up between them, they each pay about 67p, giving a total of £9 each. The £3 should appear nowhere in the calculation of money paid out. It goes sraight into their pockets. Nobody on the Science board is condescending to answer because they are all too busy rubbishing each other's qualifications or pretensions to understand anything. I just took a look at the Science board. What a shame they are all at each other's throats. Sounds like everyone there wants to be top dog. Very childish. Shame really.
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