Whic to erms bgn a f - l qu?

(a) ?,?,GN,B,U,PIK,AC
(b) ?,?,H,U,-,X,V,G,-,-,L,W,...
(c) ?,?,2,3,46,05,7,98,...
(d) ?,?,O,RM,TANG,-,F,D,-,P,L,-,-,X,_,_,J,_,_,Z,_,_,V,_,_,_
(e) ?,?,EN,CHMD,O,Z,QT,W,-,P,-,F,-,K,-,G,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,X,-,J,...
(f) ?,?,GL,TOS,CN,H,X
(g) ?,?,IE,FOR,-,H,QZ,-,ND,-

Source: The GCHQ Puzzle Book

  • 2
    $\begingroup$ Why the downvote? $\endgroup$
    – Giraffe
    Sep 11 '18 at 10:40
  • 2
    $\begingroup$ @u_ndefined Oh it's not spam! It's a puzzle :) The strange way the question is written at the start helps you solve the puzzle (a bit). $\endgroup$
    – Giraffe
    Sep 11 '18 at 10:42
  • $\begingroup$ Is the single space in (a) deliberate? (There are no spaces elsewhere in (a) or anywhere in (b) and (c).) $\endgroup$
    – Gareth McCaughan
    Sep 11 '18 at 14:44
  • $\begingroup$ @GarethMcCaughan No. I will fix the odd spacing. $\endgroup$
    – Giraffe
    Sep 11 '18 at 15:00
  • 1
    $\begingroup$ I'm pretty sure I've got the set for (d), but the ordering is another matter entirely. This seems like a pretty interesting puzzle! $\endgroup$
    – Deusovi
    Sep 11 '18 at 16:41

Whic to erms bgn a f - l qu?

I believe the rule here is that each letter can only be used once. The start of the sentence would be Whic(h) t(w)o (t)erms b(e)g(i)n ... I'm not getting much further yet, but I'm pretty sure that rule is correct.

f - l could be

first to last, with the "-" indicating a missing word.


That reasoning extends to the four lines. Each being a list of things, with repeating letters (or numbers) discarded. For example, in list 4) the fifth word (TANG) could be TANG(O), because the O is already taken. That would mean that the first two words could not contain the letters ORMTANG. No idea what the lists could mean though.

d) Is:

Quebc, Whisky It's letters on the keyboard (QWERTZ) in NATO code: Quebec, Whiskey, Echo, Romeo...

c) Is

1, -, 2, 3, 46, 05, ... It's Pascal's triangle this number triangle I forgot the name of, where you add a 1 and start and end and everything else is the sum of the two values on top. You know, the thing which goes: 1, 11, 121, 1331, 14641...

@Christoph solved a) and together with @MOehm b).

I now believe the "question" is:

Whic(h) t(w)o (t)erms b(e)g(i)n a f(irst) (to) l(ast) qu(eue)

Again, @Christoph with the good solution.

  • $\begingroup$ qu could be rot13(dhrfgvba). Also, I do not agree with your Presumably part. If that were the case then rot13(gnat) would not have existed there in the question. But I do believe you are headed in the right direction $\endgroup$
    – R.D
    Sep 13 '18 at 9:07
  • $\begingroup$ @R.D I'm pretty sure about the presumed part now. Each line is its own riddle with its own set of things and the question is just an example. $\endgroup$
    – nishuba
    Sep 13 '18 at 9:25
  • $\begingroup$ Hmm keep going. I can see what you mean now. $\endgroup$
    – R.D
    Sep 13 '18 at 9:40
  • $\begingroup$ Bah!!! I've been spending ages trying to work out the entire sequence for D. Missed that the questionis just the first two terms!!! $\endgroup$
    – Mohirl
    Sep 13 '18 at 10:00
  • 1
    $\begingroup$ Just a nitpick, but your c) is technically wrong. If you add the numbers the next number after 14641 would be 510105, and the following entries in the sequence wouldn't work out. Anyways, your answer is great, I wouldn't been able to start with mine if you hadn't done the ground work by figuring out the basic schema of the riddle! $\endgroup$
    – Christoph
    Sep 13 '18 at 12:29

Building on @nishuba's observation, namely that

every letter only appears once per set.

The question could be:

Which two terms begin each of the following sequences?
(Thanks to @Mohirl for the last word)

Set a)

RED, YeLlOW, GreeN, Brown, blUe, PInK, blACk
It's the color of snooker balls, ordered by value.

Set b). With a little help of Obi Wan Oehm:

FIRST, sECOND, tHird, foUrth, fifth, siXth, ...
The ordinals.

Set c)

1, 11, 121, 1331, 14641, 161051, ...
The powers of 11.

Set d) was solved by @nishuba.

Set e)

BULbASauR, IVYsaur, vENusaur, CHarManDer, charmeleOn, chariZard, sQuirTle, ...

Set f) was solved by @Zandar.

Set g) was solved by @MOehm.

  • 1
    $\begingroup$ I believe your second word is slightly incorrect ;) $\endgroup$
    – nishuba
    Sep 13 '18 at 9:30
  • $\begingroup$ Your solution to b) works if there is a very first entry missing. $\endgroup$
    – nishuba
    Sep 13 '18 at 9:48
  • 2
    $\begingroup$ Regarding (b): rot13(Hfr gur beqf, Yhxr!). :) $\endgroup$
    – M Oehm
    Sep 13 '18 at 9:50
  • 1
    $\begingroup$ I think the last word in the question is actually rot13(frdhraprf) $\endgroup$
    – Mohirl
    Sep 13 '18 at 10:02
  • 1
    $\begingroup$ I was brainstorming words with the letters CHMD, when the solution came to my mind. A nice feature of the riddle is that you can easily verify if a solution is correct or not, that helps a lot! $\endgroup$
    – Christoph
    Sep 14 '18 at 5:04

The answer for f) is

Golf terms for scoring par and under (although the origin of the last two may just be a random edit on Wikipedia):
PAR, BIrDiE, eaGLe, albaTrOSs, CoNdor, ostricH, phoeniX.

  • 1
    $\begingroup$ Wow, well done! No wonder looking at the usual sets of seven things didn't get me anywhere ... $\endgroup$
    – M Oehm
    Sep 14 '18 at 6:29

Partial addendum


These are the ten hardnesses of the Mohs scale:

TALC, GYPSUM, calcItE, FluORite, apatite, ortHoclase, QuartZ, topaz, coruNDum, diamond

  • $\begingroup$ This is great. How did you do it? $\endgroup$
    – Giraffe
    Sep 13 '18 at 21:25
  • 1
    $\begingroup$ QZ stands out with its rare letters, so I looked for words that have QZ, but neither N nor D in them: quiz, squeeze, equaqlize, quartz, etc. We are also looking for a set or series of ten things and the Mohs scale fits. $\endgroup$
    – M Oehm
    Sep 14 '18 at 6:13

Partial thoughts

Since the title is supposed to be somewhat of a hint, trying to complete it here-
Which two terms begins and fills question mark?
if correct, then missing letters could be clues, which are- h,w,t,e,i,n,d,i,l,s,e,s,t,i,o,n,m,a,r,k

  • 1
    $\begingroup$ That doesn't sound quite right.... "Which two terms begins..." wouldn't be grammatically correct. I suspect there's more to the title than missing letters. $\endgroup$
    – Sneftel
    Sep 11 '18 at 15:06
  • $\begingroup$ There was a small typo too. It should have been bgn not bgns. In return, I added (d). $\endgroup$
    – Giraffe
    Sep 11 '18 at 15:08

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