All Questions
Tagged with calendar-computations recreational-mathematics
7
questions
3
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Friday the $13$ths with digits adding up to $13$
Three Friday the $13$ths with digits (in yyyy-mm-dd) adding up to $13$ include 2006-01-13, 2006-10-13, and 2011-05-13.
So, how many such Friday the $13$ths (in the Gregorian calendar) are there from ...
- 10.1k
1
vote
1
answer
69
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Frequencies of gaps between years with $3$ Friday the 13ths
Years with $3$ Friday the 13ths in the Gregorian calendar usually occur with gaps of $3$ or $11$ years, except for two $6$-year gaps (between $2099$ and $2105$, and $2195$ and $2201$) and one $12$-...
- 10.1k
4
votes
2
answers
341
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Question concerning the solution of a certain calendar problem involving modular arithmetic.
A question I was given is the following:
A certain month on the calendar has 31 days, and it has an equal amount of Mondays and Wednesdays. How many different kind of days(Monday to Sunday) can be ...
- 2,821
0
votes
1
answer
131
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"New Year falls more often on Sundays than on Mondays"
This is a question from a hungarian math contest from the year 1948.
It was Saturday on the 23rd October, 1948. Can one conclude that New Year falls more often on Sundays than on Mondays?
Well, I ...
- 4,794
12
votes
4
answers
2k
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Smallest future date which involves no repetition of a digit in the format DD/MM/YYYY [closed]
What is the smallest future date which involves no repetition of a digit in the format DD/MM/YYYY for the year? What is your approach?
- 309
2
votes
2
answers
879
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Jack's birthday riddle
Anytime each of three consecutive months has exactly four Fridays, Jack's birthday will fall in one of those three months. Which month is that?
- 22.5k
3
votes
2
answers
237
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Five Fridays and Sundays on October
How to prove that if you take any 400 consecutive Octobers then exactly 14 % of those years have five Fridays and Sundays?
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