How many sig figs does this number have?

No decimal:Everything EXCEPT 0’s at the end (4100 2 sig. fig.’s)

Decimal:Everything EXCEPT 0’s at the

beginning (0.0032 2 sig. fig.’s) (1000. 4 sig. fig.’s) (1.0003 5 sig. fig.’s)

How many sig figs does this number have?

If the number is in Scientific notation:

Everything before the x 10something

(1.540 x 1017 4 sig. fig.’s) (1.2 x 1024 2 sig. fig.’s)

Count the sig. fig.’s:

1. 2002. 200.3. 200.004. 2.000 x 1014

5. 200.016. 0.000007

1

5

4

5

3

1

Adding/Subtracting Sig Figs

Line up the decimal places Draw a straight line just past the last digit they have in common.

Add/subtract Keep everything to the left of the line.

23.2 6.052+ 139.4

23.2 6.052+ 139.4 168.652 168.7

153 600+ 168 921 900

0.0097 + 0.0563 0.0660 0.0660

Multiplying & Dividing Sig Figs

Round the answer to the same number of sig figs as in the number with the fewest sig figs.

23.2 x 0.1257 = 2.91642 2.92

14.89 ÷ 0.003 = 4963.333 5000

42.7 X 0.0046 = 0.19642 0.20

407.1 / 12.3 = 33.09756 33.1

2.7 X 0.1400 = 0.378 0.38

Exact Numbers Found by:

• Counting (ex: I see 24 students in my class)

• By definition (there are 12 inches in a foot or 1000 m in 1 km)

Do not take in account any exact numbers when counting sig figs during calculations.

*so if you are dividing #cm/#pages, the #pages is exact so your final answer will have the same number of sig figs as your # cm.