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Placing Coins That Touch

Date: 8/7/96 at 0:36:10
From: mzeman
Subject: Placing Coins That Touch

How  many 20 cent coins can you put around a 20 cent coin with them 
all meeting together?

Date: 9/1/96 at 17:31:57
From: Doctor Jerry
Subject: Re: Placing Coins That Touch

I assume you have tried an experiment and found that six coins can 
surround a coin of the same size.  

If you start with a circle of radius a and then draw two more circles, 
each of radius a and drawn so that they are externally tangent to 
each other and to the first circle, you will observe an equilateral 
triangle with vertices at the centers of the three circles. So, the 
central angle is 60 degrees. This process can be repeated around the 
first circle, so that six circles in all can be placed around the 
first circle.

-Doctor Jerry,  The Math Forum
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Associated Topics:
High School Conic Sections/Circles
High School Geometry
High School Puzzles
High School Triangles and Other Polygons
Middle School Conic Sections/Circles
Middle School Geometry
Middle School Puzzles
Middle School Triangles and Other Polygons

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