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?

With 5 rods you can represent 0 - 31 different numbers. Break each number down in to it's binary equivalent and on those rods write down the number. At the top of each rod, write the number 1 - 5 representing the least to most significant bits.

For example, take the number 19. In binary

10011

So, 19 would be written on the first, second and fifth rod.

Posted by David Hanna on 2003-12-03 20:59:41