1. Significant digits

2. RULES FOR SIGNIFICANT DIGITS
1. Non-zero digits are ALWAYS significant.
Example
2. Zeros that are between other significant digits are ALWAYS significant.
Example- 3004 
3. Final zeros that occur before or after the decimal are ALWAYS significant.
Example
4. Zeros used for spacing the decimal are NOT significant.
Example

3. EXAMPLES 3 SIG FIGS 4 SIG FIGS 5 SIG FIGS 250 m/s 3150 m/s 74850 m/s
0.250 ml
3.150 ml ml ml ml ml ml ml ml ml ml ml
700 m/s
7 000 m/s
m/s
8.07 x 106 m/s
8.007 x 106 m/s
x 106 m/s

4. HOW MANY SIGNIFICANT DIGITS?X

5. ADDING & SUBTRACTING Here is the rule:
Look at all of the numbers to add/subtract and find the number with the LEAST number of sig. digs. AFTER the decimal. This is how many sig. digs. should be after the decimal in your answer.
Example
2.343
3.21
30.239
ANSWER = 30.24

6. MULTIPLYING & DIVIDING
Here is the rule:
Look at all of the numbers to multiply/divide and find the number with the LEAST number of sig. digs. This is how many sig. digs. that you should have in your answer.
Example x 2.1 = 6.762
ANSWER = 6.8