Aim: How can we perform mathematical calculations with

significant digits?

Do Now:

State how many sig. figs. are in each of the following:

1. 4.98 x 106

2. 0.00209

3. 872.010

4. 9,501,000

3

3

6

4

Addition and Subtraction

RULE: Round the answer to the least precise measurement.

Ex: 10.26

131.5

+ 12.862

Least Precise Measurement (fewest decimal places)

154.622

Round this answer to the least precise measurement (one decimal place)

Answer: 154.6

Problems

1) 109.0006

5.23

87.11

+ 9--------------------------------------------------

2) 3.862

- 0.8943

3) 123.456

7.89

+ 0.12-----------------------------------------------

4) 987.65

- 4----------------------------------------

5) 300,000,000

+ 0.45

210

2.968

131.47

984 300,000,000

Multiplication and Division

RULE: Round the answer to contain the same number of significant digits as the number with the least number of significant digits.

Ex: 36.5 / 3.414

Least number of significant digits (3)

= 10.69127124

Round the answer to 3 significant digits

Answer: 10.7

Problems

1) 27.3 / 4.2

2) 49.2 x 87.61

3) (3.1 x 108) (2.98 x 104)

4) 3.26 x 10-4 / 4.2 x 10-9

5) 107.3 x 6

6.5

4.31 X103 or 4310

9.2 x 1012

7.8 x 104 or 78,000

6 x 102 or 600

Note: It is a good idea to keep numbers in scientific notation when possible