1. Significant Figures and Conversions

2. It would be difficult to measure the width of this 2×4 to better than a millimeter.

3. Uncertainty We do not know infinite digits of a measurement
Exact numbers are known for sure
Inexact – have some question (estimates)

4. Reporting Numbers
In recorded numbers, all the digits are considered exact up until the last digit which may be off by one
8.8 ± .1
All digits including the uncertain one are called significant figures
We are fairly confident of these digits

5. Read to the correct number of significant figures

6. Read to the correct number of significant figures

7. Read to the correct number of significant figures

8. Read to the correct number of significant figures

9. Which Digits Are Significant?
Any non-zero number is significant
Any number to the left of a decimal is significant
Zeros to the right of a decimal and behind other numbers are significant
Zeros to the right of a decimal but in front of other numbers are not significant

10. How many Significant Figures in each below?
) 3440. ) )
) 1002
) 400. )
) 6000 )

11. Round each to 3 Significant Figures
31.068
2.613
81.436
149.51
143.81

12. Multiplying and Dividing
Multiply or divide the number out as normal but round the answer to the least number of significant figures in the problem

13. Solve each with correct Sig Figs
2.4 x =
94.20  =
(5.682 x 105) x (2.87 x 104) =
(2.145 x 10-5)  (6.75 x 104) =
2.5cm x km =

14. Addition and Subtraction
Add or subtract as normal but round the answer with the same number of decimal places as the quantity in the calculation having the least

15. Solve each with correct Sig Figs
5.44 –
87.3 – 1.655
2.3cm + 7.7μm m =

16. Conversions Often the units must be changed in order to do a problem
Conversion factor method is utilized
See conversion factor chart at end of the book

17. Examples How many cm in 118 in?
If there are .24L in one cup, how many liters in 26 cups?
How many L in 6.5 gal?
40 L = ________gal
850 cm = __________in
4.5 L = __________cups
How many cm2 are in 35.5 square inches?
How many cubic meters in 1575 ft3?