A while ago I created a small book with 80 Calcudoku puzzles,
ranging from easy to quite tricky, which was printed and used as
a prize in a math contest (the "Kangooroo Math" contest).
The puzzles are targeted at late primary school / early secondary school kids.
I made a new edition, with a new set of puzzles, changed design,
and published it for free as a Christmas present
https://www.calcudoku.org/calcudoku_puzzles_en.pdf (English version)
https://www.calcudoku.org/calcudoku_puzzels_nl.pdf (Nederlandse versie)(Dutch version)
edit: some typos were fixed, and the explanation edited in the English version, thanks to
ambidexter for the feedback
(
Jan 24, 2021)
The books have some (hopefully) useful solving tips, as well as puzzles for points