Decimals

A price tag reads $3.45. The 3 clearly means three dollars. But what is the 4? And the 5? They're less than one dollar each, yet they matter — skip them and the price is wrong. The dot between the 3 and the 4 is doing something important: it marks where the whole dollars end and the pieces of a dollar begin. And those pieces follow a rule you already know, just walking in the opposite direction.