1. Significant Figures

2. Uncertainty of Measurement
All measurements are assumed to be approximate with the last digit estimated.
The length in “cm” here is written as:
1.45 cm 1 2
The last digit “5” is estimated as 1/2 of the interval between 4 and 5.

3. Estimated Measurements (Cont.)1 2
Length = 1.45 cm
The last digit is estimated, but is significant. It tells us the actual length is between 1.40 cm and It would not be possible to estimate yet another digit, such as
This measurement of length can be given in three significant figures - the last is estimated.

4. Significant Figures
When writing numbers, zeros used ONLY to help in locating the decimal point are NOT significant—others are. See examples.
cm 2 significant figures
cm 5 significant figures
cm 4 significant figures
50.0 cm 3 significant figures
50,600 cm 3 significant figures

5. Pacific-Atlantic Rule=
(2) =
(5)
95.0 =
(3)
70020 =
(4)
385 =
(3)
6,000 =
(1)