1. ….or “Sig Digs”, if you prefer.
Significant Digits
….or “Sig Digs”, if you prefer.
Sometimes called
“Significant figures”
That’s right: “Sig Figs”
Anyway…..

2. First, some rules: 4 1. All non-zero digits ARE significant.
1, 2, 3, 4, 5, 6, 7, 8, 9.
Example: the number “5691” has…
_____ sig digs. 4

3. Next Rule: 6 Zeros between other sig digs ARE significant.
Example: the number “204017” has
____ sig digs. 6

4. 3rd Rule: 4 3. Zeros to the right of the decimal place and
(hold on tight- this is where it gets a little complicated…)
3. Zeros to the right of the decimal place
and
…to the right other sig digs
ARE significant.
Example:
The number “1.000” has
____ sig digs. 4

5. Last Rule: All other zeros are NOT significant.
…they are just “place holders”.
Confused?
Lets do some examples….

6. Examples: 2 4 3 .00081 has ____ sig dig(s). 100 has ____ sig dig(s).
(only) 1 4
100.0 has ___ sig dig(s). 3
54900 has ____ sig dig(s).

7. Multiplying & Dividing: So what’s the big deal?
Remember the old saying:
“A chain is only a strong as it’s…..
…weakest link”?
Same kind of idea with sig digs:

8. A calculated number is only as accurate as ….
…the least accurate measured number
that went into that calculation.
In other words:
Your answer should have no more
(and no less) sig digs than the least
number that went into that calculation.
OK- more examples….

9. 12.6 divided by 5.1 Your calculator would say…. 2.470588235 2.5
But you should only report the answer as…
2.5
(5.1 has only 2 sig digs)
Round up when appropriate.

10. One more example: Your calculator would say… 380707332
But you should only report
since has only 4 sig digs.

11. The answer is just “3”, right…?
OK- last one, really….
…how ‘bout:
2.00 x 1.500
The answer is just “3”, right…?
Nope- you need to report your answer as
3.00
(remember- answers can have no more but no less sig digs
than the least number that went into the calculation.)

12. Adding & Subtracting This time, it’s limited to
This rule is a little different.
This time, it’s limited to
the least sensitive decimal place.
So, with adding & subtracting,
you don’t need to count sig digs,
You look at decimal places!!!

13. Example:
When added gives you
HOWEVER:
Since 3.9 in the above problem only goes to
the tenths place….
You must only report your answer to
the tenths place:
18.9
Notice: you can have as many sig digs as you need, as long
as you keep to the least sensitive decimal place.

14. So to review: For multiplying & dividing: For adding & subtracting:
Count sig digs in the equation and
limit the answer to the least number.
For adding & subtracting:
Look for the least number of decimal places
and limit it that way.