It is the end of term on More or Less so we have invited two celebrity guests to join us for a Christmas numbers quiz.
Loyd Grossman is known to millions as a broadcaster and food critic. Less well known is his love of numbers.
He scored 99% in the American college board maths paper (the US university entrance exam) and he says he prides himself on never resorting to a calculator if he can avoid it.
Bonnie Greer is a playwright and novelist. She is a renowned cultural commentator, judge for numerous literary prizes and a regular on the critics panel of Newsnight Review.
She also lists as one of her hobbies in Who's Who "reading popular books on theoretical maths especially Prime Number Theory and the Riemann Hypothesis".
Hear how they get on with our quiz.
Find out how to win at Monopoly using probability theory.
Mathematicians Rob Eastaway and John Haigh share their top tips with presenter Tim Harford and help him to beat the rest of the More or Less team in record time.
The economic value of gifts
Are presents and gift vouchers worth on average more or less to their recipients than the giver paid for them?
Our reporter Ruth Alexander finds out why some economists say it is better to give cash whilst others believe it is the thought that counts.
BBC Radio 4's More or Less was broadcast on Monday 17 December 2007 at 1630 GMT.
You can e-mail us by using the form below:
Disclaimer: The BBC may edit your comments and cannot guarantee that all emails will be published.