1. Calculations with Sig Figs and Rounding
August 19, 2014

2. Rounding in calculations
Exact numbers or constants do not affect rounding
Keep all intermediate digits and round only at the end of the problem
Addition/Subtraction
Same number of digits to the right of the decimal as the original value having the fewest number of digits
Multiplication/Division
Same number of digits at the value with the fewest in the original

3. Addition and Subtraction
Count the number of sig figs to the right of the decimal =
The original value with the least amount is the number you should have in your final answer
= (calculator answer)
= 6.7 (final answer)

4. Addition and Subtraction Practice=
8.54 – = =
3.57 – =

5. Multiplication and Division
Count the number of Sig Figs in each
155 x 33 =
The original value with the least amount, will be the same number of Sig Figs in your final answer
155 x 33 = 5115 (calculator answer)
= 5100 (final answer)

6. Multiplication and Division Practice
38,736 / 4784 =
4.8 x 2.01 =
8.420 / 4.21 =
3.33 x 3 =

7. Constants do not affect final answer
Speed of light is always 3.00 x 108 m/s
If a wavelength is 25 meters how long would it take to travel one wavelength?
(3.00 x 108 m/s) / (25m) = 1.2 x 107 sec

8. Keep all intermediate digits and round only at the end of the problem=
= (calculator answer)
= 77.2 (final answer)
4.35 x 2.34 x 7.4 =
x 7.4 = (calculator answer)
= 75 (final answer)

9. Extended Problems