🚀 go-pugleaf

In article <361936B9.23D80D13@yahoo.com>, poprockz@yahoo.com wrote:
> Here's my answer:
>  Sort the 12 coins by weight min to max.
>  Check if 1st coin = 2nd then answer is last coins is fake
>   else first coin is fake.

As long as we're being silly, I can do it with no weighings at all.  Simply 
take a ruler, and tie it to a pencil in the middle of the ruler.  Place one 
coin on one end of your improvised see-saw and drop all the other coins on 
the other end from a pre-determined height.  Measure how high the coin 
jumps.  Repeat for each other coin, and the one that represents the data 
point out of line with the others is the fake.  If it jumped higher, then 
it's lighter - if it jumped lower, then it's heavier.

Or, glue each coin to a piece of elastic.  Grab all twelve pieces of 
elastic, and spin them at the same speed around your head.  One piece will 
either stretch further than the others (signalling a heavier, fake, coin), 
or stretch less (signalling a lighter, fake, coin).

Or, make a Newton's cradle with the coins, and carry out repeated 
experiments to see which coin imparts more or less momentum than would move 
one coin at the other end.  You can probably even do this by sliding coins 
across the table, if it is sufficiently smooth.  You didn't state how smooth 
the table might be, in your problem description.

(And if you're listening out there, Mr Kenny, did you ever figure out if you 
could fit a circular coin through an elliptical hole by sliding it fast 
enough down the table for Lorenz contraction to occur?)

Alun.
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