
Re: coins problem
Posted:
Jan 27, 1999 4:46 PM


See if this helps:
12 coins problem  Frans Faase http://home.wxs.nl/~faase009/Ha12coins.html
At 3:02 PM 0500 1/27/99, Helena Verrill wrote: >a little while ago, someone asked the following: > >if you have 12 coins, one of which is either >heavier or lighter than the others, the others all >being the same weight, how can you determine which >one it it, and whether it's heavier or lighter, in >three weighings. > >Well, I did't think about this problem until last >weekend when I heard it for a second time. >Anyway, it's not too hard to solve, but how about >what is the minumum number of weighings that you >need to determine which is the odd one, and whether >it's heavy or light, from n coins? >Eg, you can do 3 coins in 2 weighings, >12 coins in 3, 38 coins in 4 weighings  >I'd rather ask for what is the sequence a_n >so that a_n is the maximum number of coins such >that the odd one can be found (and said to be heavier >or lighter). I'd guess this starts 3,12,38... >but I can't find this sequence in Sloanes integer >sequences, so presumably that means 38 is not the >max you can do in 4 weighings... Anyone else tried? > >Helena
Sarah Seastone Editor, Archivist, Web Page Designer The Math Forum http://forum.swarthmore.edu/

