Why Does the Answer Key Give 188.1 for This Significant Figures Calculation?

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Discussion Overview

The discussion revolves around a significant figures calculation related to a homework problem involving the addition of three fractions. Participants are examining the discrepancy between their calculated result and the answer provided in the answer key.

Discussion Character

  • Homework-related, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant calculates the expression as 188.2, while the answer key states it is 188.1.
  • Another participant suggests not rounding off until the final step to ensure accuracy in significant figures.
  • A participant provides a detailed calculation showing intermediate results without rounding, arriving at 188.1192.
  • There is a discussion about how to determine the number of significant figures in the final answer while still adhering to the rules of significant figures in each step.
  • Some participants emphasize that it is possible to know the significant figures at each step without rounding until the end.

Areas of Agreement / Disagreement

Participants express differing views on when to apply significant figures, with some advocating for rounding only at the final step, while others discuss the implications of significant figures at intermediate stages. The discussion remains unresolved regarding the correct application of significant figures in this context.

Contextual Notes

Participants do not fully agree on the methodology for applying significant figures, and there are unresolved questions about the correct interpretation of the rules in this specific calculation.

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Homework Statement



Add the following:

(2.526/3.1) + (0.470/0.623) + (80.705/0.4326)


2. The attempt at a solution

= (2.526/3.1) + (0.470/0.623) + (80.705/0.4326)
= (0.81) + (0.754) + (186.6)
= 188.2

I have calculated the answer (using sig figs) to be 188.2, however, the answer key says it is 188.1.
 
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Don't round off until the last step.
 
Doc Al said:
Don't round off until the last step.

= (2.526/3.1) + (0.470/0.623) + (80.705/0.4326)
= (0.8148) + (0.7544) + (186.55)
= 188.1192

If I don't apply sig figs to each step, then how would I know how many sig figs there would be in the final answer?
 
You can know how many sig figs in each step and still not round off until the end.
 
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Doc Al said:
You can know how many sig figs in each step and still not round off until the end.

Ok. I see. Thank you.
 

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