I received this in my email:

Kpa nfwa jnjnbb vo Sk kizk auy phurtpijd?

Solve it.

Don't ignore the "" tag!


1 Answer 1


The answer is

How many digits of Pi have you memorized?

The solution method is:

basically a Vigenere cipher where the key is given by the digits of pi: 31415926... becoming CADAEIBF... In other words, to decrypt, send each letter back in the alphabet by a number of places given by the corresponding digit of pi.

Cryptography of the day:

Happy Pi Day!

And to answer the question:

personally, I've memorised up to 3.14159265358979... (but for this puzzle we need up to 3.14159265358979323846264338327950 - up to the first zero exactly!)

  • $\begingroup$ I was going to (jokingly) correct your mistake with 'memorised', but I see you have already fixed it. I have memorized it to the exact same place as you. $\endgroup$ Commented Mar 14, 2020 at 13:20
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    $\begingroup$ @LannyStrack The funny thing is I've memorised it to exactly that place because of a mnemonic I read in, all of places, a fantasy novel. One character is a mathematician and says: "Yes, I know I think admirably of myself. Cocky, but right! Problems? [His name]'s supreme." The extra 9 is just bonus. $\endgroup$ Commented Mar 14, 2020 at 13:23
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    $\begingroup$ Another mnemonic that goes exactly as far as you say you've learned is one that I, curiously enough, first saw in a sci-fi-ish novel (Rudy Rucker's White Light; it's very strange). "How I need a drink, alcoholic of course, after the heavy lectures involving quantum mechanics." I learned a lot more places than that while in secondary school, for no reason other than that I could. I think I still remember all the 10-digit chunks I learned it in, but not necessarily what order they appear in... $\endgroup$
    – Gareth McCaughan
    Commented Mar 14, 2020 at 13:38
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    $\begingroup$ @Rand al'Thor: Wow. I feel a sense, literally, of wonder about the novel mnemonic. Cordially express gratitude. $\endgroup$ Commented Mar 14, 2020 at 13:51
  • $\begingroup$ See also puzzling.stackexchange.com/questions/61918/… for another handy mnemonic ;) $\endgroup$
    – Rubio
    Commented Mar 15, 2020 at 21:34

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