Quick Significant Figures Problem

In summary, the conversation discusses the incorrect answer given to a problem with multiple significant figures. The correct answer should be 2.02 x 10^3, but the answer key states 2.0 x 10^3. The discrepancy may be due to the uncertainty in the numbers used in the problem.
  • #1
Lori

Homework Statement


)(9.66x10^-1) + (5.1x10^2) -8.77+2.8 ) / ((8.333x10^-2)(3.001))

Homework Equations


None

The Attempt at a Solution



my answer does not match the answer key which is 2.0 x 10^3.[/B]
When i did the problem , i ended up get 3 SF answer. The numerator simplies to 504.996 where the sigfigs should be 3 because 0 is the least number of decimals. The denominator is simplified to 0.25007333 where the sigfigs is 4 because 4 is the least number of sig figs. So, when i divide, i get 2019.391672. Since, 3 is the least number of Sigfigs, the answer should be 2.02 x 10^3.

BUT, the answer key is saying otherwise! What am i doing wrong? Am i using the rules right?
 
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  • #2
Lori said:

Homework Statement


)(9.66x10^-1) + (5.1x10^2) -8.77+2.8 ) / ((8.333x10^-2)(3.001))

Homework Equations


None

The Attempt at a Solution



my answer does not match the answer key which is 2.0 x 10^3.[/B]
When i did the problem , i ended up get 3 SF answer. The numerator simplies to 504.996 where the sigfigs should be 3 because 0 is the least number of decimals. The denominator is simplified to 0.25007333 where the sigfigs is 4 because 4 is the least number of sig figs. So, when i divide, i get 2019.391672. Since, 3 is the least number of Sigfigs, the answer should be 2.02 x 10^3.

BUT, the answer key is saying otherwise! What am i doing wrong? Am i using the rules right?
I get ## 2020## even without calculator, so if I was asked, I'd, too, answered ##2.02 \cdot 10^{3}##:
$$((9.66x10^-1) + (5.1x10^2) -8.77+2.8 ) / ((8.333x10^-2)(3.001)) = (1 + 510 -8 +2 )/ (\frac{25}{3}\cdot 3 \cdot \frac{1}{100}) = 505/(\frac{1}{4}) = 2020$$
However, we don't have information about the accuracy of the single numbers, so their uncertainty could lead to only one significant digit. With three it should be ##2.02##.
 
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Likes Lori
  • #3
Hey Lori :)

Doesn't 5.1x102 have 2 significant digits?
After the additions and subtractions, it dominates the other terms in the numerator.
That makes the suggested rounding 2.0x103.
What does the answer key say?
 
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Related to Quick Significant Figures Problem

1. What are significant figures?

Significant figures are digits in a number that carry meaning in terms of accuracy or precision. They represent the certainty of a measured or calculated value.

2. How do I determine the significant figures in a number?

To determine the significant figures in a number, start counting from the first non-zero digit and continue until the end of the number. Trailing zeros after a decimal point are significant, but leading zeros are not.

3. How do I round a number to the correct number of significant figures?

To round a number to the correct number of significant figures, identify the least significant digit and look at the next digit. If the next digit is 5 or more, round up the least significant digit. If it is less than 5, leave the least significant digit as is. Then, drop all digits to the right of the desired number of significant figures.

4. Can I use significant figures in multiplication and division?

Yes, significant figures are used in multiplication and division. The result should have the same number of significant figures as the factor with the fewest significant figures.

5. How do I handle significant figures in addition and subtraction?

In addition and subtraction, the result should have the same number of decimal places as the number with the fewest decimal places. This may require adding or subtracting extra zeros to maintain the correct number of decimal places.

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