magic rectanglemagic squarechallenging Dad to guess what the magic square and the magic rectangle arefun multiplication shortcutsfavourite Brilliant.org problem (Simon has actually carried out an experiment with in real life marbles is a sack to see whether the probability predicted is correct)
challenging Dad with the Brilliant.org problemchalenging Dad with the Brilliant.org problem (Simon has also taken this problem to show to his French teacher)
Geeks out of the box 