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AN EASY METHOD TO AVOID PRODUCING MISLEADING RESULTS

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Presentation on theme: "AN EASY METHOD TO AVOID PRODUCING MISLEADING RESULTS"— Presentation transcript:

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


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