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Rounding
General Chemistry I and II Lab Manual
Dakota State University
page 232 of 232
Rounding
In the significant figures section, I intentionally left out how to round numbers.
The rules for rounding are usually a little more involved than most people realize (not
much, just a little).
Remember that the purpose of rounding is to try to minimize errors in
the final results.
If we always round down, we know our answer will always be too low;
if we always round up, the answer will always be too high.
Through proper rounding
techniques, we will get a mix of answers that are either too low or too high, and the errors
have at least a fighting chance of canceling each other out so our final answer is close to
the actual answer.
(1)
Numbers greater than 5 always round up.
Thus, to 4 significant figures,
22.347 becomes 22.35.
Keep in mind that any number greater than five will round up;
thus 654.235000000004 rounds up to 654.24 to 5 significant figures, because
0.005000000004 is greater than 0.005, even though it is not by much.
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This note was uploaded on 01/27/2012 for the course CHM 2045 taught by Professor Josephwalter during the Fall '11 term at Dakota State.
 Fall '11
 JosephWalter
 Chemistry

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