Significant Figures – Definition, Examples, Rules, Rounding
7 minutes read
Created: January 1, 2024
Last updated: January 12, 2024
Welcome to another exciting journey into the vibrant world of mathematics brought to you by Brighterly! At Brighterly, our mission is to illuminate the path of learning for children, breaking down complex mathematical concepts into comprehensible and engaging chunks. Today, we turn our spotlight on a fascinating yet often misunderstood topic: significant figures.
Understanding significant figures is akin to possessing a magical key, a key that unlocks the doorway to precision and accuracy in mathematics. Be it simple arithmetic or intricate scientific computations, the concept of significant figures plays a pivotal role. This comprehensive guide will provide an indepth exploration of what significant figures are, why they’re important, and how to work with them accurately and confidently.
What Are Significant Figures?
In the world of mathematics, significant figures represent more than just random digits. They provide a way to show the precision of a number or the accuracy of a measurement. For instance, if a child measures the length of a table using a meter stick, the significant figures of the measurement tell us how precisely they have measured it. A simple concept, yet it has profound implications in both basic arithmetic and complex scientific computations.
Significant Figures Definition
Significant figures are defined as all the numbers that provide meaningful information about the precision of a measurement or calculation. These can include both nonzero digits (like 1, 2, 3, 4, etc.) and zeros, depending on their position in the number. For instance, in the number 123.45, all five digits are significant because they each contribute to the accuracy of the number.
What Are the Rules for Significant Figures?
Determining significant figures involves a set of rules that help us identify which digits in a number are significant and which aren’t. Here are the primary rules to remember:
 Nonzero digits are always significant.
 Any zeros between significant figures are significant.
 Leading zeros, or those that precede all nonzero digits, are not significant.
 Trailing zeros, or those at the end of a number, are significant only if the number has a decimal point.
Understanding these rules will help children perform mathematical operations with greater precision and accuracy.
How to Round Off Significant Figures
Rounding off to a specific number of significant figures is a skill often used in math and science to simplify numbers without losing too much accuracy. To round off a number:
 Identify the last significant figure in the number you want to keep.
 Look at the digit immediately to its right.
 If that digit is less than 5, leave the last significant figure unchanged. If it’s 5 or greater, increase the last significant figure by 1.
Multiplication and Division with Significant Figures
When multiplying or dividing numbers, the rule for significant figures is straightforward: the result should have as many significant figures as the original number with the least significant figures. It’s crucial to understand this rule to maintain precision in mathematical operations.
Addition and Subtraction with Significant Figures
In addition and subtraction, the result should be reported to the same decimal place as the least accurate measurement. In other words, it should have the same number of decimal places as the number with the smallest number of decimal places.
Rounding Significant Figures
After performing operations with significant figures, the final step is often to round the result. The rules for rounding are the same as when rounding off a specific number of significant figures, ensuring that the result is as precise as the least precise number used in the calculation.
Solved Examples on Significant Figures
Let’s apply these rules with some examples:

Example 1: If we multiply 3.45 (3 significant figures) by 2.7 (2 significant figures), the result is 9.315. However, we must round this to 2 significant figures, so the final answer is 9.3.

Example 2: If we add 123.4 (4 significant figures) and 56.78 (4 significant figures), the result is 180.18. As the numbers we added have 1 and 2 digits after the decimal point, our result should have only one digit after the decimal point. Hence, the final answer is 180.2.
Practice Questions on Significant Figures
Now that we understand the rules, here are some practice questions:
 Round the number 0.004567 to three significant figures.
 Multiply 3.45 by 2.7 and express your answer in the correct number of significant figures.
 Add 123.4 to 56.78 and express your answer in the correct number of significant figures.
Conclusion
In the constellation of mathematical concepts, significant figures shine with their importance in ensuring precision and accuracy in calculations. While understanding them might seem challenging at first, remember that every new skill requires patience and practice. Here at Brighterly, we believe in the power of stepbystep learning, turning the complex into the comprehensible, the baffling into the familiar. As your child continues to explore the wonders of mathematics, mastering significant figures will prove to be an invaluable tool in their learning journey. Until our next mathematical adventure, keep the curiosity alive and keep learning brighter and better with Brighterly!
Frequently Asked Questions on Significant Figures
What are significant figures?
Significant figures are the digits in a number that carry meaningful information about its precision. They include all nonzero digits, zeros between nonzero digits, and trailing zeros in a decimal number.
How to identify significant figures in a number?
Identifying significant figures involves understanding a few rules: Nonzero digits are always significant. Any zeros located between significant figures are significant. Leading zeros are not significant, while trailing zeros are significant only if the number has a decimal point.
What are the rules for rounding off to significant figures?
Rounding to significant figures involves looking at the digit immediately to the right of the last significant figure you want to keep. If that digit is less than 5, leave the last significant figure unchanged. If it’s 5 or greater, increase the last significant figure by 1.
How to perform mathematical operations with significant figures?
For multiplication and division, the final answer should have as many significant figures as the number with the least significant figures in the calculation. For addition and subtraction, the answer should have as many decimal places as the number with the least decimal places in the operation.
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