1. AN EASY METHOD TO AVOID PRODUCING MISLEADING RESULTS
SIGNIFICANT FIGURES
AN EASY METHOD
TO AVOID PRODUCING
MISLEADING RESULTS

2. IT’S EASY! IT’S FAST! Two Rules are used: One for Adding & Subtracting
One for Multiplying & Dividing

3. When adding or subtracting
Note accuracy of measurements
(nearest .1? .01? .001?)
Answer can be no more accurate than the LEAST accurate number
that was used to calculate it.

4. For Example:
5.50 grams
grams
14.1 grams

5. OR ml ml
2.39 ml --> 2.4 ml

6. When multiplying or dividing
You must COUNT significant figures
The answer can have only AS MANY
significant figures as the LEAST of the numbers used to get it

7. Here is a one sentence rule for counting sig figs:
All digits ARE significant except
Zeros preceding
a decimal fraction
and
Zeros at the end of a number
containing NO decimal point

8. For Example: .0045 has 2 significant figures
but has 5 significant figures

9. AND 45.50 has 4 signifcant figures while 45.5000 has 6 sig figs
and has only 1 sig fig

10. Numbers with no decimal are ambiguous...
Does 5000 ml mean exactly 5000?
Maybe.... Maybe Not!
So 5000, 500, 50, and 5 are all assumed to have 1 significant figure
If a writer means exactly 5000, he/she
must write or x 103

11. How many sig figs in each #?

12. Now let’s do some math..... (round answers to correct sig figs!)
g g
answer: 6.55 g
Did you need to count sig figs? NO!

13. Try this one.... 4.80 ml - .0015 ml answer: 4.80 ml
(one might say .0015
is insignificant
COMPARED TO 4.80)

14. Now try these... 5.0033 g / 5.0 ml answer: 1.0 g/ml
Did you have to count sig figs?
YES!

15. Here’s a tougher one..... 3.0 C/s x 60. s/min x 60. min/hr =
answer: C/hr --> C/hr
Note: standard conversion factors never limit significant figures--
instruments and equipment do.

16. THAT’S ALL THERE IS TO IT!
Use least accurate measurement when adding and subtracting
Count sig figs when multiplying and dividing