In volume 8 of In Another World With My Smartphone, Touya (the MC) encounters ruins containing riddles. Whilst the novel explains the questions and answers to most of them, one of them has me confused:

"Please follow the rules of the current calculation. In this system, what does X equal?" 36 = 1, 108 = 3, 2160 = 2, 10800 = X.

Touya claims the answer was straightforward and proceeds. But, whilst it may have been straightforward to him, I don't get it. If required, I can supply the answer he gives, but, I didn't want to spoil it.

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    I suggest checking out puzzling.stackexchange.com site for puzzles and riddles like this one. Even if it comes from anime, I don't think this is the best place to ask, and not being able to find "riddle" tags is an indication of that :p Also, perhaps include some screenshots or pictures if you can and if it you think it would help. – Hakase May 10 '18 at 6:29
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    congrats! i believe you are the first person to ask a question requiring the creation of a new tag that needed all 35 characters – Memor-X May 10 '18 at 6:43

While there are probably many possible answers, the most common answer is

10800 = 5, or X = 5.


  1. "0" is 1,"1" is 0, etc. (the puzzle usually avoids "4" because it's ambiguous)

  2. Count the loop on each digit.

  3. Only "0", "6", "8" and "9" have loop(s) on their digits.


"10800" has 5 loops; 3 from "0" and 2 from "8", thus X = 5.

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