Talking about significant figures, my Physics textbook lists 5 rules for determining significant figures. 1) All nonzero digits are significant. 2) Zeros to the right of nonzero digits in a number containing a decimal point are significant. 4) Zeros to the right of the decimal point, but the left of the first nonzero digit (such as .000324) are significant. 5) Zeros between nonzero digits (such as 26,007) are significant. I'm stuck on #3, which says: Zeros at the end of a number without a decimal point are ambiguous. It then lists a few examples: In 6800 there are two significant digits. In 10,000 there is one significant digit. In 650 there are three significant digits. Why is the zero in 650 significant, but not in 6800 and 10,000? Sorry if this question is confusing. Thanks for any and all help! :-)