Maths was never my strong point (in a weak field of strong points) but I can heartily recommend Alex Bellos's new book, Alex's Adventures in Numberland. Here's an example of the sort of question he addresses:
The answer (which feels to my literalist mind a bit of a cheat) is here. (This puzzle is also fascinating.)
Sort of maths-related, there are some diverting little brainteasers here, including this one:
I have two children. One is a boy born on a Tuesday. What is the probability I have two boys?
The answer (which feels to my literalist mind a bit of a cheat) is here. (This puzzle is also fascinating.)
Sort of maths-related, there are some diverting little brainteasers here, including this one:
In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on floor above.You may move any of the switches but you may only go upstairs to inspect the bulbs one time. How can you determine the switch for each bulb with one inspection?
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4 comments:
The lightbulbs one took me a while to work out (it's heat related?)
Try this from pedagon.net:
A galleon is ignited on the high seas.
All sailors, except for the captain, leave aboard life boats.
The captain dives and swims under water for 90 metres. He hears an explosion.
When he surfaces, he immediately hears another explosion.
The captain rejoins a life boat and is pulled aboard by the sailors.
The captain mentions that he heard two explosions.
The sailors state that they only heard one explosion.
Both captain and sailors are telling the truth.
Question: How is this possible?
Sound travels faster in water anon? Mind you, that still sounds slightly unrealistic, bearing in mind he was only 90m away. Would the difference be noticeable?
Don't introduce any more problems... I'm still trying to work out why the answer to the probability of "2 boys" is not 1/2 :)
AIUI...
- the first boy is a given
- there is no connection between the sex of the two offspring, they are independent events
- "on Tuesday" is irrelevant
The net result is the answer boils to down to the probability of the sex of a single child.
So, assuming an equal likelihood of girl/boy the answer is 1/2.
According to Bellos, it's actually 13/27 (as opposed to 1/2) Keith (though, as I said, it's a slightly artificial answer, I think).
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