You have five coins, apparently alike, but actually of different weights. You also have a two arm scale.

Can you manage to sort the coins in ascending order, using the scale only seven times?

Bonus question: can it be done in fewer weighings?

(In reply to re: Full solution by Erik O.)

In e.g.'s method, you would have weighed the 3 vs the 4 and found the 4 heavier.  You would then have weighed the 1 vs the 2 and found the 2 heavier.  Then you would have weighed the 4 against the 2 and found the 4 heavier, so you'd know 4>2>1 and 4 > 3, so that the letters that would apply are d=4, b=2, a=1. (It's at this point that the labels are applied, and all the inequalities represent a weighed determination.)

Posted by Charlie on 2004-06-02 13:48:58