Christmas puzzles: the solutions

Chalkdust

2 January 2021

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To celebrate Christmas this year we released a sequence of three linked puzzles on Christmas Eve, Christmas Day, and Boxing Day. If you haven’t had a chance, do give these puzzles a go! If you have tried these puzzles and would like to see the solutions, please read on.

Puzzle #1: Christmas tree sudoku

If you haven’t tried solving a so-called thermo sudoku before, getting an intuition for how the thermometers work is key. Notice that if a $1$ lies on a thermometer it must lie on the bulb, and if a $9$ lies on a thermometer it must lie at the end. This gives a good way to start the puzzle, looking at the third row from the bottom where can a $1$ go? Once you are about a third of the way into this puzzle, it more-or-less turns into a normal sudoku and is relatively straightforward to complete. Contrary to normal practice when designing a sequence of puzzles like this, this was possibly the hardest of the three puzzles. That’s why we made it so that you could still solve puzzle #2 without solving this one.

Hence we see that $\alpha=3$, $\beta=1$, $\gamma=4$, $\delta=9$, $\varepsilon=4$, $\zeta=2$, $\eta=1$, $\theta=8$, and $\lambda=4$. Why did we miss out $\iota$ and $\kappa$? They were on Santa’s naughty list after what they did to $\mu$!

Puzzle #2: A Christmas nonogram

Nonograms can be quite fun, especially when they draw a timeless Christmas scene as this one does, although by their nature it’s very difficult to make them really challenging as logic puzzles. As was claimed it is entirely possible to solve this puzzle without knowing the values of $\alpha$–$\lambda$, you should have finished up with this design, I wonder what it could be?

Puzzle #3: Colouring by numbers

The final puzzle builds on the design above, colouring in some of the remaining squares to reveal a mathematical winter scene. Below is the solution, with all the numbers you had to find indicated. Below that is the final design without the messy details of the puzzle.

We do hope you enjoyed having a go at our puzzles, let us know how you got on via Twitter @chalkdustmag, and we wish you and your family a very merry Christmas, and a happy new year from the whole Chalkdust team!