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Five Pins on a Board (Posted on 2023-09-27) Difficulty: 3 of 5
Five pins are randomly nailed to a square board (according to a uniform probability distribution), and a rubber band is stretched completely around them to form a convex shape.

What is the probability that the rubber band is in the shape of a quadrilateral?

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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If the randomization area were a circle rather than a square Comment 3 of 3 |
(In reply to No Subject by Charlie)

To see what the stats would be if the original area for the randomized points were a circular disk rather than a square the selection criteria were added that points outside the circle would not be chosen, leaving the randomization uniform, via:

  for i=1:5
    x(i)=-10;
    while (x(i)-.5)^2+(y(i)-.5)^2>.25
      x(i)=rand; y(i)=rand;
    end
  end
  
 The statistics were:
 
 cts =
            0           0     9499303    54885616    35615081     
 trial =
    100000000
 ans =
     0        0          0.09499303         0.54885616       0.35615081

 triangle       9.50 %
 quadrilateral 54.89 %
 pentagon      35.62 %

  Posted by Charlie on 2023-09-27 22:17:10
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