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The Watchdog (Posted on 2004-10-28) Difficulty: 5 of 5
A watchdog is tied to the outside wall of a round building 20 feet in diameter. If the dog's chain is long enough to wind half way around the building, how large an area can the watchdog patrol?

See The Solution Submitted by Erik O.    
Rating: 3.4000 (5 votes)

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This Works, Too | Comment 28 of 29 |

There is a ratio of radii which also realises the correct answer, viz. L^3 / 3r ... that is:

Area of horns (A) = Length of chain ^3 / 3 silo radii 

A = 10pi^3 / 30
A = 31006.27668 / 30
A = 1033.542556
Semicircle Area (S)  = 1550.313834
A + S = total area 
1033.542556 + 1550.313834 = 2583.85639

  Posted by CeeAnne on 2006-04-27 13:09:48
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