Bellringer 9/11/09

How many significant figures?

1) 0.0022) 0.00303) 1.0020

4) 45.05) 2.010

Today’s Objective

• Students will be able to work with significant figures

Rules for Calculating with Sig Figs

• Addition or Subtraction

• Rule: The final answer should have the same number of digits to the right of the decimal as the measurement with the smallest number of digits to the right of the decimal.

Example

• 97.3 + 5.85 = 103.15 which rounds off to 103.2

Rules Continued

• Multiplication or division

• The final answer has the same number of significant figures as the measurement having the smallest number of significant figures

Example

• 123 x 5.35 = 658.05 which rounds off to 658

Rules for rounding

• Round down when:

• The digit following the last sig fig is a 0,1,2,3, or 4

• The last sig fig is even and the next digit is 5

Rules for rounding

• Round up when:

• The digit following the last sig fig is a 6,7,8, or 9

• The last sig fig is odd and the next digit is 5