In primary school, you probably came across "place value". You know, where you look at the "ones column" and the "tens column" and then the "hundreds column", and so on. Why do we pick the ones column, the tens column and the hundreds column (and so on)? This is because ten is a useful number, for a number of reasons. Look at your hands. You have ten fingers (I'm sure that *certain people* object that this is in fact eight fingers and two thumbs). Also consider how easy it is to multiply by ten – you just add a zero on the end.
- `125 * 10 = 1250`