While in Norway doing some maths shows I was given a tshirt and a puzzle. Both are very mathematical. If you have not tried a "Prisoners in Hats Puzzle" before, I explain the basic version. If you have seen it before, I also give a variation which I had not come across previously. Give it a go! MathsJam: http://mathsjam.com/ Math-Jam: http://math-jam.com/ If you want to discuss this puzzle somewhere more comfortable, it seems I have a fledgling subreddit: https://www.reddit.com/r/MattParker/ Music by Howard Carter Design by Simon Wright MATT PARKER: Stand-up Mathematician Website: http://standupmaths.com/ Book: http://makeanddo4D.com/ Nerdy maths toys: http://mathsgear.co.uk/