Adding and Subtracting Significant Figures

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SUMMARY

The discussion focuses on the rules for adding and subtracting significant figures in mathematical operations. The key takeaway is that the result should reflect the least precise measurement in the calculation. In the example provided, 43.4 - 22 - 3, the correct answer is reported as 20, adhering to the significant figures rule where the least precise number (3) dictates the precision of the final result. Additionally, the use of root mean square (RMS) for error calculation is mentioned, yielding an answer of 18.4 ± 0.7.

PREREQUISITES
  • Understanding of significant figures in mathematics
  • Basic arithmetic operations (addition and subtraction)
  • Familiarity with error analysis techniques
  • Knowledge of root mean square (RMS) calculations
NEXT STEPS
  • Study the rules for significant figures in multiplication and division
  • Learn about error propagation in scientific calculations
  • Explore advanced topics in statistics related to significant figures
  • Review practical applications of significant figures in laboratory settings
USEFUL FOR

Students in mathematics or science courses, educators teaching significant figures, and professionals involved in precision measurements and data analysis.

cvc121
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Homework Statement


Hi,

To add or subtract sig figs, it is to my understanding that the answer is reported so that it reflects the least precise number.

For the example 43.4 - 22 - 3, would I report my answer as 18 or 20?
Thanks. Any help is very much appreciated!

Homework Equations

The Attempt at a Solution


The least precise number is 3 but I am not sure if I would report my answer with 1 or 2 sig figs. I am guessing that my answer should be 20 since it has only one significant figure as well.
 
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Been a long time since I did such a thing formally but as I recall the normal practice is to say that your error is the RMS of the individual errors, which in this case would be sqrt((.05*2 + .5*2 + .5*2)/3) = .7 so your answer is 18.4 +/- .7
 

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