What does 1 significant figure mean?

Metimes we do not always need to give detailed answers to problems - we just want a rough idea. When we are faced with a long number, we could round it off to the nearest thousand, or nearest million. And when we get a long decimal answer on a calculator, we could round it off to a certain number of decimal places.Another method of giving an approximated answer is to round off using significant figures.

1. Any non zero digit is significant. exg 1234=4 sig figs

2. Zeros between digits (bracketed zeros) are always significant. exg 1.01.001= 6 sig figs

3. zeros at the end of the answer when no decimal point are not significant exg 500=1 sig fig

4. zeros at the end of the answer when a decimal point is specified are significant. exg 500.=3 sig figs
2.00=4 sig figs