Answer:
There is at
least one Friday the 13th every
year.
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Complete
Solution:
There are 14 different calendars. There are seven possible
calendars for non-leap years: one with January 1 on each
day of the week. Leap years give seven more calendars,
for a total of 14. For example, if January 1 is on a Wednesday,
you have the following list: |
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January 1
January 13
February 1
February 13
March 1
March 13
April 1
April 13
May 1
May 13
June 1
June 13 |
Wednesday
Monday
Saturday
Thursday
Saturday
Thursday
Tuesday
Sunday
Thursday
Tuesday
Sunday
Friday |
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Because June 13 is a Friday, you can stop.
The chart below shows the total number of Friday the 13ths
for all 14 calendars. |
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| When
January 1st
is on |
Non-leap Year months with a Friday the 13th |
Leap
Year months with a Friday the 13th |
| Monday |
April,
July |
September,
December |
| Tuesday |
September,
December |
June |
| Wednesday |
June |
March,
November |
| Thursday |
February,
March, November |
February,
August |
| Friday |
August |
May |
| Saturday |
May |
October |
| Sunday |
January,
October |
January,
April, July |
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