This is the penultimate match before we find out who is the World’s Most Interesting Mathematician (2019 edition, of the 16 people who were asked to take part and were available in July).
For the second semi-final, from group 3 it’s Sophie Carr up against the winner of group 4, Becky Warren. The pitches are below, and at the end of this post there’s a poll where you can vote for your favourite bit of maths.
Take a look at both pitches, vote for the bit of maths that made you do the loudest “Aha!”, and if you know any more cool facts about either of the topics presented here, please write a comment below!