Monday, February 18, 2008

into my world

A few photos from my day...

Perhaps one of the most unusual cars I've ever seen - giraffe print?!

Brooks Dye Works - makes me ponder what it was like to live in the industrial age

St. Werburgh's park - the most unusual old school public toilet I've ever seen, just a stone's throw from my house

Now, here's a puzzle for all of you people who's brains work these things out better than myself. Barnes family, I have every faith in all of you to be able to figure this out. (There will be a prize for the winner.)

Three friends have a meal in a restaurant. The waiter arrives with the bill, which is for £30, and the friends put in £10 each to cover it. When the waiter gets to the till, he finds that he has overcharged them - the bill for the meal should have been £25 - so he takes out five £1 in change. Now, being a slightly dishonest man, he decides to give the friends £1 each, so they end up paying £27 between then, and he pockets the remaining £2. But £27 plus £2 is £29, not £30. Where has the extra £1 gone?

I am sure the answer should be simple and straightforward but neither I, nor a number of my friends can work it out! I look forward to hearing your solutions.


PelleasAnthor said...

The £30 is a red herring. It just happened to be the amount of money they parted with originally. It is all still 'in the system'. If you think of there being 30 £1 coins number c1, c2, etc.

Initially, c1..c30 are handed to the waiter. c1..c25 are put in the till and c26, c27, c28 are handed back to the customers, while c29 and c30 are put in the waiter's pocket. The meal actually cost the customers £29 not £30 so there is no need to consider the £30 in the final reckoning.

snailsnail said...

oooo... pipped to the post ;-)

PelleasAnthor said...

What I should also have said in my original comment is that the problem includes an example of double counting. I.e., adding the waiter's £2 to the £27 whereas, of course, the £27 the customer's paid already includes that £2.

I suspect this is a characteristic of all such problems.