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Friday The 13th Riddle

Friday The 13 Riddle - 17 june

Many people would think Friday the 13th will be an unlucky day. Is it possible that there is no Friday on 13th through the whole year? How many Fridays at 13th can we have in a year at most? Can you calculate it out?

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16 comments:

  1. This is known as Virus attack day

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  2. Friday falls on 13th at least once and a maximum of 3 times a year. This happens when a month starts with a sunday. I don't think any calculation or a fact is involved here. or is it?

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  3. Leap year starting on sunday ll have 3 fridays on 13th day of the month.

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  4. each month has 4 weeks + 0,1,2 or 3 odd days(extra days apart from the regular 28 days). these odd days will have a role in deciding the day.
    no. of odd days in an year are as follows(monthly basis):
    3,0 or 1,3,2,3,2,3,3,2,3,2,3
    last one is december..again, it will play no role as a different year will start after it.
    now check if the sum of odd days for consecutive months is a multiple of 7.
    we observe that, in a leap year jan to march gives 3+1+3=7 odd days=week= friday on april 13 again if jan 13 is a friday. continue in this fashion, (april may june=2+3+2=7 again) july 13 also comes out to be a friday.. and no other combination gives a friday again..so a maximum of 3 fridays.(infact, check 2012 calender)
    in a non leap year if feb 13 is friday, then march 13 is friday(coz of 0 odd days in feb) and from march onwards, 3+2+3+2+3+3+2+3=21(march to oct), so november 13 is a friday.. 3 friday 13th again.
    the aim is to add consecutive odd days to make a multiple of 7. 2+3+2 is an easy choice to pick which occurs for apr,may,june and sept,oct,nov.

    minimum one friday 13th will always be there

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  7. friday the 13th doesn't exist, its just a myth.

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    Replies
    1. you're stupid

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    2. AHAHAHAHAHAHAHAHAHAHAHAHAHA!!!!!!!

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    3. there have been several fridays with the date of 13. How can a day be a myth?

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  8. i dont know plz give me correct answer someone...

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    Replies
    1. We can calculate out how many days there will be for the 13th on each month if we count from the beginning of the year (January 1). Then we divide total days by 7 to get the remainders. We also need to consider the leap year. Through the whole year we had all kinds of remainders, from 0 to 6. The minimum of occurence for all the unique remainders was 1. It means that we have at least one Friday on 13th. In a regular year, the best chance you can get 3 Fridays on 13th, which are in February, March and December because the remainders of these 3 months are 2. In a leap year, the best chance you also can get 3 Fridays on 13th, which are in January, April and July because the remainders of these 3 months are 6.

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