Brain Teasers
Unlisted Phone Numbers
There is a town where 5% of all people living in the town have unlisted phone numbers. If you selected 100 names from the phone book, on average, how many of these people would have unlisted phone numbers?
Answer
Zero. You are selecting names from the list, so they are all listed.Hide Answer Show Answer
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The riddle did not state that there was not roster of all town members somewhere.
easy peasy lemon squeesy
very good!
Apr 13, 2002
For clarity, it probably should have said, "If you selected 100 names from the phone book". This might make it too easy, but I agree with the above comment, that without clarifying what list, this answer isn't correct.
no.. you should say that they are looking in the phone book
How about if the names are listed, but the phone numbers are not.
However, if you select 100 names, you are selecting them from 'a list'. Therefore, they are 'listed'...am I making sense at all?
my answer was "assuming you got them from the phone book, none" - i don't know where this riddle is set, but in australia there's such a thing as an electoral roll (because voting is compulsory everyone over 18 is *supposed* to be on it), you can get a list of all the people over 18 living in an area, whether their phone numbers are "listed" ones or not...
I was thinking along the same lines - from a phone book, none, but there are many lists you could select names from, or you could select names from your mind - of people you know. Considering that, with it being 100 people I said 5
you never said he picked from a list, he picked 100 names
It would be better if it said that he picked the names out of a phone book. It was still good.
Its good actually.
Amusing, but unfortunately incorrect.
If you had a phone book of my home town, you might pick me, because I am listed in the book. However, I also have another number which is unlisted. The question asked "how many of these people would have unlisted phone numbers?" not "how many of the numbers you call were unlisted?"
If you had a phone book of my home town, you might pick me, because I am listed in the book. However, I also have another number which is unlisted. The question asked "how many of these people would have unlisted phone numbers?" not "how many of the numbers you call were unlisted?"
I like this!
The only problem is that when I tell it to young people the concept of the phone book is getting unfamiliar and once you start explaining phone books, unlisted numbers, etc, you're giving it away. They all just use cellphones.
The only problem is that when I tell it to young people the concept of the phone book is getting unfamiliar and once you start explaining phone books, unlisted numbers, etc, you're giving it away. They all just use cellphones.
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