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Grid Polygons

 
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Griffin
Daedalian Member



PostPosted: Mon Feb 25, 2002 9:19 pm    Post subject: 1 Reply with quote

Joe has a grid that consists of dots in rows and columns, place one unit apart. By connecting these dots, Joe can create a variety of polygons. In creating a particular polygon, Joe's pencil goes through n dots. The polygon completely encloses m dots. In terms of n and m, what is the area of the polygon? Proof?



[This message has been edited by Griffin (edited 02-25-2002 04:20 PM).]
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dethwing
DeTheeThaw



PostPosted: Mon Feb 25, 2002 10:09 pm    Post subject: 2 Reply with quote

i have no idea, but i'm wondering if he draws in straight lines, or can he do curves? Or does it not matter?
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mith
Pitbull of Truth



PostPosted: Mon Feb 25, 2002 10:20 pm    Post subject: 3 Reply with quote

(n+2m-2)/2 seems to work. Don't have a clue how to prove it though.
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quercitron
Don't trust Robinson



PostPosted: Mon Feb 25, 2002 10:20 pm    Post subject: 4 Reply with quote

How about (n/2 + m - 1)

The proof is tricky though.
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quercitron
Don't trust Robinson



PostPosted: Mon Feb 25, 2002 10:21 pm    Post subject: 5 Reply with quote

yeah, mith has the same answer I do
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mith
Pitbull of Truth



PostPosted: Mon Feb 25, 2002 10:24 pm    Post subject: 6 Reply with quote

maybe some sort of induction, but there's no way you are getting me to spend time writing it up

time for class
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mith
Pitbull of Truth



PostPosted: Mon Feb 25, 2002 10:32 pm    Post subject: 7 Reply with quote

Griffin, you should post more. I always enjoy your puzzles.
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tigg
Daedalian Member



PostPosted: Mon Feb 25, 2002 10:35 pm    Post subject: 8 Reply with quote

Pick's Theorem
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Griffin
Daedalian Member



PostPosted: Tue Feb 26, 2002 3:10 am    Post subject: 9 Reply with quote

Mith - When I come up with a good puzzle, I post it.

Anyway, thankyou tigg for the link. I had a feeling when I stumbled across this relation that it was probably a famous theorem of some sort.
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tigg
Daedalian Member



PostPosted: Tue Feb 26, 2002 1:39 pm    Post subject: 10 Reply with quote

Glad to be a help, Griffin.
And nice job too, if you discovered it on your own.

You must like playing around with that stuff. Reminds me of me when I was in high school. I remember I discovered Pascal's triangle when I was in seventh grade, and I was all proud of myself. Some time later I was disappointed to find that Pascal discovered it several hundred years before. ("Hey- that's not Pascal's triangle. That's my triangle!") Oh well.

I'm 33 now and still think math is cool. Some things don't change.
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