Significant figures are the important numbers to concentrate on
Significant figures are the ones which contribute to the value.
The museum exhibited pictures of significant female figures who had contributed to our way of life over the last 100 years.
A digit is significant if it contributes to the value of a number:
0.000730 The only significant figures are 7 and 3
30743 The significant figures are all of them: 3, 0, 7, 4 and 3
6000 The significant figures are all of them: 6, 0, 0 and 0
608 The significant figures are all of them: 6, 0 and 8
The order of significance
36736 3 is the first significant figure, 6 is the second significant figure.
Another illustration is:
0.00083124 8 is the first significant figure.
3 is the next significant figure.
This project must be read in conjunction with Mammoth Memory How to remember rounding.
Example 1
Make 373,158 correct to 1 significant figure.
What this really means is round 373,158 to 1 significant figure. So rounding rules apply.
373,158 Round to 1 significant figure.
373,158 Underline the digit (first significant figure)
373,158 Look next door
7 It’s five or more so you must round up.
400,000 3 becomes 4 and all the numbers to the right become zero.
Answer:
373,158 correct to 1 significant figure = 400,000
Example 2
Correct 0.00346 to 1 significant figure.
What this really means is round 0.00346 to 1 significant figure so rounding rules apply.
0.00346 Round to 1 significant figure.
0.00346 Underline the digit (3 is the first significant figure).
0.00346 Look next door
4 It’s not 5 or more. It’s four or less so IGNORE.
0.003 Keep underlined number the same. Change all the numbers to the right to a zero.
Answer:
0.00346 to 1 significant figure is 0.003
Example 3
What is 0.00068341 to 2 significant figures?
What this really means is round 0.00068341 to 2 significant figures. So rounding rules apply.
0.00068341 Round to 2 significant figure.
0.00068341 Underline the digit (8 is the second significant figure).
0.00068341 Look next door
3 It’s not 5 or more. It’s four or less so IGNORE.
0.00068000 Keep underlined number the same. Change all the numbers to the right to a zero.
Answer:
0.00068341 to 2 significant figures is 0.00068
Example 4
Change 8.983 to 2 significant figures.
What this really means is round 8.983 to 2 significant figures so rounding rules apply.
8.983 Round to 2 significant figure.
8.983 Underline the digit (9 is the second significant figure).
8.983 Look next door
8 It’s 5 or more. So you must round up.
9.0 9 becomes 10.
NOTE:
Add one to the previous column
Answer:
8.983 to two significant figures is 9.0
