Significant Figures Not all numbers matter…

Significant Figures Definition: Digits of a number that are relevant when doing mathematical calculation. Significant figures are useful so we know when to “cut off” the amount of digits used in answering a problem. Just because it’s on the calculator, doesn’t mean it has to be part of the written answer…

Rules for Significant Figures Most figures are significant There are 2 basic rules for when a digit, or “figure” in a number isn’t significant. Rule #1: If a “0” is: a) at the end of a number AND b) THERE’S NO DECIMAL POINT then those 0’s aren’t significant.

Rule #1- Examples Some of the digits here are significant and some are not: 240, significant NOT significant Significant

Rules for Significant Figures Rule #2: If a “0” is at the BEGINNING of a number, it is NOT significant

Rule #2- Examples Some of the digits here are significant and some are not: NOT significant significant NOT Significant significant

Practice On your white board, write down the number of significant digits for each number, then hold your board up facing the teacher.

Practice 23061

Practice 26,000

Practice 26,000.0

Practice 26,

Practice 03.14

Practice

Using Significant Figures We use significant figures in math to know how “much answer” to use. For Example: The number goes on forever, you need to know how many decimal places to use.

Addition and Subtraction The answer has the least amount of numbers after the decimal as the numbers you are adding together.

Example Consider the problem: Two places after the decimal Three places after the decimal Six places after the decimal

Example Consider the problem: Two places after the decimal Three places after the decimal Six places after the decimal Two places after the decimal in the answer.

Multiplication and Division The answer matches the smallest number of significant digits as the numbers you are multiplying or dividing together.

Example Consider the problem: 120 x Two significant digits Three significant digits Needs Two significant digits

Example Consider the problem: 120 x Two significant digits Three significant digits Two significant digits This number gets rounded off and the last digit becomes a 0

Practice Complete the worksheet on Significant Figures for your classwork today.