Counting Counters

Problem | Solution | Printable page |
Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

1 counter, 1 yellow surrounded by circle of 6 blue counters, above surrounded by 12 red counters Take a counter and surround it by a ring of other counters that MUST touch two others.
How many are needed?		 line of counters: 1 yellow, 2 blue, 3 red, 4 green, 5 light blue
Imagine surrounding this ring with more counters.
How many counters are needed?
Were you right?
What about a bigger ring?
And another? And another?
Or why not just lay them down according to some rule?
What will be the $30$th counter to be laid?
The $100$th? The $200$th?

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Published March 2003.