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 Magic Rods (Posted on 2003-11-11)
You need to make a set of five rods for a magic trick, with numbers on them ranging from 1 to 31 inclusive. Then you ask people to pick a number and show you only the top number of whatever rods it is on. From that you have to guess which number the person picked. This has to be done within a few seconds and isn't a matter of remembering what numbers are on them.

What numbers should be on each of the five rods?

 Submitted by Lewis Rating: 4.0000 (7 votes) Solution: (Hide) The numbers should be: Rod 1: 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31 Rod 2: 2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31 Rod 3: 4,5,6,7,12,13,14,15,20,21,22,23,28,29,30,31 Rod 4: 8,9,10,11,12,13,14,15,24,25,26,27,28,29,30,31 Rod 5: 16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31 This uses the same idea as the binary system. All you do is add up the first numbers of the rods that have the number on. It works becuase the first number of each rod are 1,2,4,8 & 16, and using those numbers you can make any numbers from 1 to 31. For example, to make 25 you use the numbers 1,8 and 16, which are rods 1,4 and 5, so 25 is only written on those three rods.

 Subject Author Date Solution here Christopher Kostelec 2003-12-15 23:01:10 My solution David Hanna 2003-12-03 20:59:41 Solution paige 2003-11-26 23:29:34 Why so complicated? Nelson 2003-11-12 03:22:57 re: The top number? Dan 2003-11-12 02:58:35 Spare the rod, spoil the magician Dan 2003-11-12 02:39:32 solution Tristan 2003-11-11 18:59:48 re: The top number? SilverKnight 2003-11-11 15:55:29 Clue S 2003-11-11 15:45:16 The top number? Charlie 2003-11-11 15:40:32 ever so slight improvement Lee 2003-11-11 15:03:54 re: Full Solution SilverKnight 2003-11-11 13:45:34 Full Solution SilverKnight 2003-11-11 13:42:45

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