An Introduction To Significant Figures

And uncertainty, and error, and precision. If I had to teach significant figures, I'd start with this joke:

A visitor at the Royal Tyrell Museum asks a museum employee: “Can you tell me how old the skeleton of that T-Rex is?”
“It is precisely 60 million and three years, two months, and eighteen days old.”
“How can you know that with such precision?!”
“Well, when I started working here, one of the scientists told me that the skeleton was 60 million years old – and that was precisely three years, two months, and eighteen days ago…”