What’s the importance of zero, and how was it discovered? How do scientists calculate Pi’s infinite digits? Why do so many people find maths difficult – and what’s the most difficult thing in maths? CrowdScience takes on a whole bunch of questions sent in by high school students in Spain. Like many children all over the world, their school is currently closed due to the coronavirus lockdown, but lessons continue at home. So how are their studies going, and can CrowdScience help out? We attempt to answer some of their trickiest maths questions, with the help of mathematicians Katie Steckles and Matt Parker, and mathematical biologist Kit Yates. Presenter: Marnie Chesterton. Producer: Cathy Edwards (Photo: A boy studying. Credit: Getty Images)