SIGNIFICANT FIGURES
The number of significant figures refers to the number of digits reported for the value of a measured
or calculated quantity, indicating the precision of the value.
Rules for identifying the number of significant figures in a number.
1. All digits are significant except zeros (zeros may or may not be significant)
2. Placeholder zeros are not significant. Placeholder zeros would disappear if the
number is placed in scientific notation. (Ex: 0.00025 has two significant figures 2 and 5)
3. Terminating zeros ending to the left of the decimal point may not be significant. When the
decimal point is not shown (Ex: 2000) you must assume that the zeros are NOT significant.
4. Zeros are significant when they trail a number to indicate precision in the number.
For
example 0.05678000 ( the zeros to the left of 5 are not significant, but the three zeros following
the 8 are, thus the digit contains seven significant figures)
5. Zeros trapped between any two significant digits are significant. Ex: 5008 and 500.1
Find the number of significant digits in the following:
PROBLEM
ANSWER
1.
0.025
_____________
2.
54000
_____________
3.
0.005670
_____________
4.
2.40 x 104
_____________
5.
5007.00
_____________
6.
0.508
_____________
7.
0.0058363
_____________
8.
0.0600
_____________
9.
34000.00
_____________
10.
10200
_____________
ANSWERS TO SIGNIFICANT FIGURES
1.
2 – the zeros 0.025 are placeholders zeros only
2.
2 – the zeros in 54000 are ambiguous since the decimal is not shown
3.
4 – the 0.00 part is for place holder and the trailing zero is significant
4.
3 – the zero indicates precision
5.
6 – the zeros 5007.00 are trapped and 5007.00 indicate precision
6.
3 – the zero 0.508 is place holding and 0.508 is trapped
7.
5 – the zeros 0.0058363 are place holding
8.
3 – the zeros 0.0600 are place holding and 0.0600 indicate precision
9.
7 – the zeros 34000.00 indicate precision and 34000.00 are trapped
10.
3 – the zeros 10200 are ambiguous and 10200 is trapped