Unit 1 Metric system, significant figures, factor label ...

All non-zero numbers are significant. Zeroes between two non-zero numbers are significant. The (0) is significant. Zeroes to the right of a non-zero number and to the left of an understood. Decimal are not. significant. In the number 2000 with no decimal actually written, the three zeroes are only placeholders to show the magnitude of the number. ................
................