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Ducks in a pond (Posted on 2023-01-24) Difficulty: 3 of 5
3 ducks have landed in a circular pond. What is the probability there is a diameter such that the semicircle on one side contains all of them?

Repeat for 4 ducks.

Note: consider the ducks to be randomly chosen points in a circle.

No Solution Yet Submitted by Jer    
Rating: 5.0000 (2 votes)

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Some Thoughts 4 ducks as a simulation | Comment 6 of 17 |
Results seem also to verify p = 1/2 for 4 ducks:

ct=0; hit=0;
a=0;
for trial=1:100000000
        b=360*rand; c=360*rand; d=360*rand;
        ct=ct+1;
        set=sort([a b c d]);
        aa=set(1);bb=set(2);cc=set(3);dd=set(4);
        diff=[bb-aa cc-bb dd-cc  aa-dd+360];
        if max(diff)>180
          hit=hit+1;
        end      
end
disp([hit ct hit/ct])

runs with 1 million, 10 million and 100 million trials:

               fits on one side         trials             fraction
>> ducksInAPond
                    499033             1000000            0.499033
>> ducksInAPond
                   4997068            10000000           0.4997068
>> ducksInAPond
                  50007263           100000000          0.50007263

  Posted by Charlie on 2023-01-24 11:15:22
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