When you have a math problem that involves more than one operation—for example, addition and subtraction, or subtraction and multiplication—which do you do first?  Example: 6 – 3 x 2 = ?

  • Do you do the subtraction first (6 – 3 = 3) and then the multiplication (3 x 2 = 6)?
  • Or do you start with the multiplication (3 x 2 = 6) and then subtract (6 – 6 = 0)?

PEMDAS

In cases like these, we follow the order of operations. The order in which operations should be done is abbreviated as PEMDAS:

  1. Parentheses
  2. Exponents
  3. Multiplication and Division (from left to right)
  4. Addition and Subtraction (from left to right)

(One way to memorize this is to think of the phrase Please Excuse My Dear Aunt Sally.)

  • In the above example, we’re dealing with multiplication and subtraction. Multiplication comes a step before Subtraction, so first we multiply 3 x 2, and then subtract the sum from 6, leaving 0.

NOTE: An exponent refers to the number of times a number is multiplied by itself. For example, 2 to the 3rd (written like this: 23) means:  2 x 2 x 2 = 8.  23 is not the same as 2 x 3 = 6.  Remember that a number raised to the power of 1 is itself.


About the Author:

Michael Martin has more than 35 years of experience in systems design for broadband networks, optical fibre, wireless and digital communications technologies.

He is a Senior Executive with IBM Canada’s Office of the CTO, Global Services. Over the past 14 years with IBM, he has worked in the GBS Global Center of Competency for Energy and Utilities and the GTS Global Center of Excellence for Energy and Utilities. He was previously a founding partner and President of MICAN Communications and before that was President of Comlink Systems Limited and Ensat Broadcast Services, Inc., both divisions of Cygnal Technologies Corporation (CYN: TSX).

Martin currently serves on the Board of Directors for TeraGo Inc (TGO: TSX) and previously served on the Board of Directors for Avante Logixx Inc. (XX: TSX.V). 

He serves as a Member, SCC ISO-IEC JTC 1/SC-41 – Internet of Things and related technologies, ISO – International Organization for Standardization, and as a member of the NIST SP 500-325 Fog Computing Conceptual Model, National Institute of Standards and Technology.

He served on the Board of Governors of the University of Ontario Institute of Technology (UOIT) and on the Board of Advisers of five different Colleges in Ontario.  For 16 years he served on the Board of the Society of Motion Picture and Television Engineers (SMPTE), Toronto Section. 

He holds three master’s degrees, in business (MBA), communication (MA), and education (MEd). As well, he has diplomas and certifications in business, computer programming, internetworking, project management, media, photography, and communication technology.