answers for 24 questions

[Desardes]

place your wild or intellectually-based guesses answers

[joeschmoe]

I propose the guy perform a binary search for her number. the possible numbers range from 000-0000 to 999-9999. taking out the dashes and then treating the number as a value, we have 10 million possibilities (0 to 9,999,999). the guy could ask her "is your number less than or equal to 5,000,000?" if she says yes, he can say "is your number less than or equal to 2,500,000?" if she said no, he can say "is your number less than or equal to 3,750,000?" and so on. since 2^24 is 16,777,216, this line of questioning would successfully determine a single value from 10 million possibilities. however, 23 questions would only distinguish 8,388,608 possibilities. this means he'd have to ask one more question.

a neat application of this idea is looking up a word in a dictionary. since there are approximately a quater of a million words in the Oxford English Dictionary, you should be able to find the word you seek in just 18 page flips (if the words were numbered and you knew the alphabet) because each time you can exclude half the searchable area.

[MalcomBanned4?]

got my vote