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Friday the 13th (Posted on 2004-08-13) Difficulty: 4 of 5
Which day of the week (Sunday, Monday, etc.) is the probability largest to fall on the 13th of a random month, in a random year?

Or is this probability the same for each day of the week?

See The Solution Submitted by SilverKnight    
Rating: 3.5000 (4 votes)

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Solution Solution Comment 13 of 13 |

Considering the  400 year period, from 2001 to 2400, having regard to the Leap Years, a rigorous calculation yields the following probabilities, P(d) corresponding to a given day of the week(d)

d...................P(d)  
Monday..........14.2708 %
Tuesday..........14.2708  %
Wednesday.....14.3125 %
Thursday........14.25 %
Friday............14.3333 %
Saturday........14.25 % 
Sunday..........14.3125 %

From the above table,  it is observed that the probability of 13th being Friday is marginally higher compared to the other six d.o.w.'s.

Edited on August 3, 2007, 12:06 pm
  Posted by K Sengupta on 2007-05-07 12:52:58

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