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Wednesday 22 November 2017

GCHQ quiz solution: the full answers - but can you understand them?

GCHQ has published the full solution to its devilishly hard Christmas quiz, though the answers may leave you as baffled as the questions

Part of the GCHQ Christmas quiz, which has stumped the world's puzzlers Photo: GCHQ
Part of the GCHQ Christmas quiz, which has stumped the world's puzzlers Photo: GCHQ
GCHQ's cryptographers set what proved to be an unsolvable quiz

Gordon Rayner

GCHQ has published the full solution to its mind-bending Christmas quiz, but the answers may leave you just as baffled as the questions.

Some of the questions had layer upon layer of answers to them, while other questions were hidden to all but the most eagle-eyed puzzlers.

GCHQ even admitted that one “hidden clue” in its infamous Christmas puzzle was not a clue at all, but a simple typographical error.

Code-breakers the world over spent endless mental energy trying to work out why a crossword clue which should have been listed as 27 across was actually listed as 17 across, thinking there was some vital significance to the number 17 or 27.

In fact, said GCHQ, it was “unfortunately a typo”, adding: “Apologies for the confusion.”

Not that the 600,000 people who attempted the quiz needed any extra confusion. As GCHQ revealed the full solution to the fiendish puzzle it disclosed that at least one question was “not terribly fair” because it had so many hidden answers, while another had two possible solutions, which left many “unhappy” entrants looking for hidden meanings that were not there at all.

Three people have been chosen as winners out of the 30,000 who sent in their answers. Each will receive a book about the wartime codebreaker Alan Turing and a GCHQ paperweight.

So here are the questions, and the answers, in full, with explanatory notes from GCHQ.

Question 1: Where


Puzzlers had to answer the first four sections of the quiz correctly (see below) to get to the all but impossible part 5. All of the answers in part 5 are a single word or a string of letters.


The Solution:


Question 2: Sum

A straightforward algebra problem. Or is it?


The Solution:


 GCHQ said of The Sum: "The Sum in Question 5 caused the most confusion among players. Almost everyone got the obvious answer xiv, and quite a few got two additional answers l and xx based on interpreting the x as a multiplication sign. Based on the title, they then ‘summed’ the three solutions – by coincidence, the result 84 = lxxxiv can also be obtained by concatenating the three solutions.

"There were many theories about what was going on with speculation of solutions involving Leonardo da Vinci or Louis XIV!

"No-one found the four additional intended answers involving further reinterpretation of x as a multiplication sign, perhaps indicating that this was not a terribly fair question. "


Question 3: Algebraic

Use a combination of algebra and chess pieces to fill in a series of chess boards. Unless you know the meaning of the word abelian you will also need a dictionary to hand.


 The Solution:


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