Significant Figure Rules

In this tutorial, we’ll discuss significant figure rules, which are essential in mathematics, particularly when working with measurements. Understanding significant figures helps maintain precision and accuracy in calculations. We’ll cover the primary rules and provide examples to illustrate each step.

What are Significant Figures?

Significant figures, also known as significant digits, are the digits in a number that carry meaningful information. These digits contribute to the precision and accuracy of a measurement or calculation. Significant figures are crucial in scientific and engineering applications, where the reliability of measurements is vital.

Significant Figure Rules

There are several rules for determining the number of significant figures in a given number. We’ll go through each rule and provide examples for clarity.

Rule 1: Non-Zero Digits

All non-zero digits (1, 2, 3, 4, 5, 6, 7, 8, and 9) are always considered significant.

Example 1:

Number: 456

Significant Figures: 3 (All digits are non-zero and significant)

Rule 2: Interior Zeroes

Zeroes located between non-zero digits are always significant.

Example 2:

Number: 3007

Significant Figures: 4 (The zeroes between the 3 and the 7 are significant)

Rule 3: Leading Zeroes

Zeroes that precede non-zero digits are not significant. They only indicate the position of the decimal point.

Example 3:

Number: 0.00482

Significant Figures: 3 (The leading zeroes are not significant)

Rule 4: Trailing Zeroes in a Decimal Number

Zeroes at the end of a number and after the decimal point are significant.

Example 4:

Number: 4.500

Significant Figures: 4 (The trailing zeroes after the decimal point are significant)

Rule 5: Trailing Zeroes in a Whole Number

Zeroes at the end of a whole number without a decimal point are ambiguous and can be considered either significant or not significant, depending on the context. When possible, use scientific notation to clarify the number of significant figures.

Example 5:

Number: 1200

Significant Figures: Ambiguous (Could be 2, 3, or 4 significant figures)

In scientific notation:

1200 = 1.2 x 10^3 (2 significant figures)

1200. = 1.200 x 10^3 (4 significant figures)

Rounding with Significant Figures

When performing calculations, it’s essential to round your answers to the appropriate number of significant figures. Here’s how to round off numbers according to the significant figure rules:

1. Identify the last significant digit in the number.
2. If the digit immediately to the right of the last significant digit is 5 or greater, round the last significant digit up. If it’s less than 5, leave it as is.
3. Remove all digits to the right of the last significant digit.

Example 6:

Number: 3.8572 (rounded to 3 significant figures)

Step 1: The last significant digit is 8.

Step 2: The digit to the right of 8 is 5, so round 8 up to 9.

Step 3: Remove the remaining digits.

Rounded Number: 3.86

Final Thoughts

By understanding and applying these significant figure rules, you can ensure that your mathematical calculations remain accurate and precise. It’s essential to keep in mind that the number of significant figures in your result should match the number of significant figures in your input data, as rounding can introduce errors if not done correctly.

Significant figures are crucial in mathematics and science, especially when working with measurements. By following the rules outlined above and rounding to the appropriate number of significant figures, you can maintain precision and accuracy in your calculations.