Answer:
It’s ambiguous (trailing zeros for a number without a decimal point may or may not be significant), but absent additional information I would say that it has one significant figure: the leading digit 1. The trailing zeros serve only to scale the number, not to add significant figures.
This is according to the usual rules for determining significant figures:
* Non-zero digits are always significant.
* Any zeros between two significant digits are significant.
* A final zero or trailing zeros in the decimal portion ONLY are significant.
Explanation:
Note that the term significant figures only makes sense when there is uncertainty involved (such as with a measurement result). As a mathematical number, 100 (or any other number) is an exact quantity and the concept of significant figures doesn’t apply.
If you want the measurement to be 100 with three significant figures (implying an uncertainty of ±0.5 ), you could write it as 100. (with a trailing decimal point) or, less subtly, as 1.00×102 , or (even better) with an explicit uncertainty such as 100±0.5 or “100 to three significant figures".
