A friend sent me this riddle and I can't figure out a solution:

January = 251017
February = 25628
March = 81335
April = 12145
May = 251353
June = 51064
July = 251074
August = 20186
September = ?

So the question is:

What number is September?

He said this question was taken from an FBI exam but I doubt that.

  • $\begingroup$ Is 'Juli' a typo? $\endgroup$ – JMP Nov 22 '18 at 12:33
  • $\begingroup$ Yeah im german so sorry for that $\endgroup$ – Vongarnichts undStuff Nov 22 '18 at 12:36

The answer is


To form the number take

(i) the location in the alphabet of the last letter, R=18,
(ii) the location in the alphabet of the first letter, S=19,
(iii) the position of the month in the calendar, September=9,
(iv) the number of letters in the name of the month, September=9,

and concatenate 18+19+9+9 = 181999

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  • $\begingroup$ This seems to be the right answer i will accept it in an hour so other people can have a go $\endgroup$ – Vongarnichts undStuff Nov 22 '18 at 12:45
  • $\begingroup$ @Strawberry August is 20+1+8+6=20186, by the same reasoning. The code for each month is formed in the same way. $\endgroup$ – hexomino Nov 22 '18 at 14:23

The answer is:



digit of last letter in Alphabet in the month (R = 18)
digit of first letter in Alphabet in the month (S = 19)
number of the month in the year (9)
number of letters in the name (9)

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  • 4
    $\begingroup$ Welcome to Puzzling.SE! But this puzzle was already answered before you. $\endgroup$ – Hugo Woesthuis Nov 22 '18 at 19:34



First: last letter of Month digit r = 18
Then: first letter of Month s = 19
Next: number of Month September = 9
Last: count the letters of the Month = 9

Did I pass?

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  • 2
    $\begingroup$ Welcome to Puzzling SE. Remember to check if other people have already posted the solution you intend to or if a solution has already been accepted. In this case the answer you have was posted a few hours ago by someone else and been accepted. $\endgroup$ – gabbo1092 Nov 22 '18 at 21:09
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    $\begingroup$ Yes, @cedricvaernewyck, it is. $\endgroup$ – Rupert Morrish Nov 22 '18 at 21:13
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    $\begingroup$ First of all, there is no way to really know who voted on your question and there is no benefit in trying to guess anyways as no one can change someone else's vote except the person who made it. Secondly, Votes are used to indicate level of usefulness, effort and research put into a question or answer. An answer that has already been posted by someone else shows minimal research and effort as they didn't look at the page even (and may have simply copied) and even if they did come to it on their own, it ultimately isn't useful or helpful to anyone else as it doesn't contribute anything new. $\endgroup$ – gabbo1092 Nov 22 '18 at 21:15
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    $\begingroup$ Try not to take it personally (I get it can be hard not to sometimes) but votes are simply a way of filtering the obscene amount of content on this site. Just try to learn from your mistakes and you'll get the hang of it. Also if you want to learn more about the site and get your first badge check out the tour at this link: puzzling.stackexchange.com/tour $\endgroup$ – gabbo1092 Nov 22 '18 at 21:19
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    $\begingroup$ @gabbo1092 thanks for the explanation! $\endgroup$ – Cedric Nov 22 '18 at 21:24

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