# Plus Magazine

Issue 25The **Riemann Hypothesis** is probably the hardest unsolved problem in all of mathematics, and one of the most important. It has to do with prime numbers - the building blocks of arithmetic. Nick Mee, together with Sir Arthur C. Clarke, tells us about the patterns hiding inside numbers.

One million dollars is waiting to be won by anyone who can solve one of the grand mathematical challenges of the 21st century. In the second of two articles, Chris Budd looks at the well-posedness of the **Navier-Stokes equations**.

To study a system, mathematicians begin by identifying its most crucial elements, and try to describe them in simple mathematical terms. As Phil Wilson tells us, this simplification is the essence of **mathematical modelling**.

If you had a crystal ball that allowed you to see your future, what would you arrange differently about your finances? *Plus* talks to the Government Actuary, Chris Daykin about the **pensions crisis**, and how actuaries use statistical and modelling techniques to plan for all our futures.

Whether you love maths or hate maths, your opinions on the subject were probably formed early. So primary teachers have a vital role to play in promoting mathematical skills. *Plus* meets **primary teacher and maths coordinator** Maureen Matthews.