You are a biochemist, working with a 12-slot centrifuge. This is a gadget that has 12 equally spaced slots around a central axis, in which you can place chemical samples you want separated. The slots on the centrifuge are numbered 1 through 12 clockwise (and clock-like).

           12  1
        11        2

      10            3
             °
       9            4

         8        5
            7  6

When the machine is turned on, the samples whirl around the central axis and do their thing. To ensure that the centrifuge runs smoothly, the samples must be distributed in the 12 slots such that it is balanced evenly.

Can you use the centrifuge to run 5 samples?

For example, if you have four samples, they may be placed in slots 1, 4, 7, and 10 to balance the centrifuge.

(In reply to Are biochemist really that smart?. by ajosin)

It only takes a few seconds to prepare a water sample.  There are probably plenty of test tubes just lying around, and they don't need to be clean.  The tap water from the nearest sink suffices.  The dummy sample can even be reused.  It makes just as much sense to complain about wasting precious seconds pondering silly balancing puzzles.

Posted by Tristan on 2005-04-14 22:02:56