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 My favorite number (Posted on 2003-06-16)
You are trying to guess my favorite number. I tell you it is from 1-100 somewhere and is an interger. You can guess anything you like and I will tell you whether my number is higher or lower then your guess. What is the smallest number of guesses you can make to make sure you will get my number, no matter what it is?

Assume that I don't lie to you about the greater or less than value.

 Submitted by Jon Rating: 2.6667 (6 votes) Solution: (Hide) The logic to this game starts by going half way between the limits you know for the number. The first logical guess would be 50. Say my number is 17. So the guesser would say 50(1 guess), and I would say lower. G(short for guesser)=25(2), me=lower. G=12(3), me=higher. G=19(4), me=lower. G=16(5) me= higher. G=18(6), me=lower. G=17(7), I say right. 7 is the least number of guesses required to guess any number. Obviously you can get lucky, but this way works better most of the time. This is also proved by using powers of 2. 2^1=2 2^2=4 ....... 2^6=64 2^7=128 this means that these same 7 guesses could be used for every number between 128 and 1. I like 1-100 better.

 Subject Author Date Solution Dej Mar 2008-06-17 04:59:10 answer K Sengupta 2007-11-12 02:29:00 re: The Trick (Full Solution) Ady TZIDON 2006-01-18 10:18:11 re: Possible solution? Ady TZIDON 2006-01-18 10:10:08 hopefully this site is so confusing Viet 2003-07-14 07:03:04 re: Is this right? DJ 2003-06-19 16:53:58 So hard riddler 2003-06-19 12:21:28 Is this right? Gamer 2003-06-19 05:54:07 re: The Trick (Full Solution) Gamer 2003-06-19 05:45:47 The Trick (Full Solution) DJ 2003-06-17 17:24:10 Some Halve it, some don't Sanjay 2003-06-16 09:46:30 My way not_so_einstein 2003-06-16 07:31:26 re(2): Possible solution? DJ 2003-06-16 06:29:30 re: Possible solution? Gamer 2003-06-16 05:57:42 Possible solution? fwaff 2003-06-16 03:09:46

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