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Math Lesson 2.1.9 - Applications of Significant Figures

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Welcome to our Math lesson on Applications of Significant Figures, this is the ninth lesson of our suite of math lessons covering the topic of Rounding and Significant Figures, you can find links to the other lessons within this tutorial and access additional Math learning resources below this lesson.

Applications of Significant Figures

Significant figures have a wide range of applications in practice. For example, if the perimeter P of an equilateral triangle is 8.00 cm and we want to calculate the side length L, we write

L = P/3 = 8.00 cm/3 = 2.6666..cm

However, it is clear that we cannot express the result in this way, as we cannot be that precise in measurements. This means we have to express the result at only two decimal places as this is the tiniest division of units. Therefore, e must write the result at three significant figures: one before the decimal point and two after it. Hence, we must write the result as L = 2.67 cm.

Example 4

The sides of a quadrilateral are 3.2 dm, 5 dm, 4.32 dm and 7.29 dm. Calculate the perimeter of this quadrilateral and express the result in the correct number of significant figures.

Solution 4

The perimeter of a quadrilateral is the sum of all sides. Hence, we have

P = 3.2 dm + 5 dm + 4.32 dm + 7.29 dm = 19.89 dm

However, it makes no sense to write the result like this, as one of the sides (the 5 cm one) is measured in whole decimetres, so we must write the result in decimetres as well to ensure it fits the least precise measurement. Therefore, we must round the result to the nearest whole number, i.e. P ≈ 20 dm. Hence, it is written in one significant figure, as the number taken as a reference to determine the precision of result (the number 5) has only one significant figure.

Apparently, the rounded result seems less accurate than the original. However, in science we prefer to be sure in the correctness of our findings. Therefore, it is better to round the result and give an approximate value to the correct result than to make groundless assumptions.

More Rounding and Significant Figures Lessons and Learning Resources

Approximations Learning Material
Tutorial IDMath Tutorial TitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
2.1Rounding and Significant Figures
Lesson IDMath Lesson TitleLessonVideo
Lesson
2.1.1What is Rounding
2.1.2Rounding to the Nearest Ten
2.1.3Rounding to the Nearest Hundred
2.1.4Rounding to the Nearest Thousand
2.1.5Explaining Rounding in the Number Axis
2.1.6Other Types of Rounding
2.1.7Significant Figures
2.1.8Rules of Significant Figures
2.1.9Applications of Significant Figures

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  7. Continuing learning approximations - read our next math tutorial: Upper and Lower Bounds. Intervals and Segments

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