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If you’re a regular listener to Radio Wales you’re probably familiar with the knotty little puzzle which is Eleri Sion’s daily 2.45 Teaser. In this week’s programme Adam is in conversation with the man behind it:ÌýGareth Ffowc Roberts, Professor Emeritus of Education at Bangor University.

Gareth has devoted his career to making mathematics accessible, interesting and enjoyable to generations of students and teachers. And now he’s getting everybody else engaged through his puzzles on radio and social media.

Adam talks to him about how we can all learn to love mathematics. They also discuss Wales’ contribution to the study of the subject through great mathematicians like Robert Recorde and William Jones. And Gareth sets a special teaser exclusively for Science Café:

Question: Imagine that you’re organizing a table tennis knockout competition with fourteen competitors. In the first round you’ll have seven matches and seven competitors will be knocked out. In the second round, with an odd number of competitors, one of them will have to have a bye into the next round. The rounds carry on until one competitor – the overall winner – is left. How many matches will there have been in total? Now, how many matches would you need if there had been 100 competitors?

Answer: 13 matches. There’s actually a pattern here: however many competitors, the number of matches is always the number of competitors minus 1. And here’s why: every match knocks out one competitor, so in a pool of 14 competitors you need 13 matches to leave one winner. So,you need 99 matches to find the winner in a pool of 100 competitors.

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