chemistry: Significant figure rules

In this unit we covered a concept called significant figures. Significant figures are each of the digits of a number that are used to express it to the required degree of accuracy, starting from the first nonzero digit.

http://passyworldofmathematics.com/significant-figures/

There are several rules that go along with significant figures which can be seen above in the picture. The first rule is that all non-zero numbers are always significant. The second rule is that all zeros between non-zero numbers are always significant. The third rule is that all zeros which are simultaneously to the right of the decimal point and at the end of the number are always significant. The last rule is that all zeros which are to the left of the written decimal point are in a number greater than ten are always significant.

Number	# Significant Figures	Rule(s)
48,923	5	1
3.967	4	1
900.06	5	1,2,4
0.0004 (= 4 E-4)	1	1,4
8.1000	5	1,3
501.040	6	1,2,3,4
3,000,000 (= 3 E+6)	1	1
10.0 (= 1.00 E+1)	3	1,3,4