Chris Smith: Today’s problem is all about the number 2. 2 is a number with some very special powers. Let me show you what I mean. In maths, when we talk about powers, we mean how many times 2 has been ...

Let’s say we invite you to invest £1,000 in our new and brilliant business. We promise you an impressive return on your money, and all we ask is that you persuade a few of your friends to invest the ...