I recently read the Common Core standards for Math for grade 6, which is where the concept of variable appears to be introduced. The standard in question reads:
Write, read, and evaluate expressions in which letters stand for numbers.
I tweeted this out, and one person responded with this observation:
@davidwees in d/dx[f(x)]=mx+b ...d, f, dx, f, x, m, and b all have completely different meanings, and only m and b "stand for numbers"— John Chase (@mrchasemath) October 27, 2013
Clearly this definition of variable is limited, and possibly misleading.
How do you define variable with your students? How do you introduce the topic?
David is a Formative Assessment Specialist for Mathematics at New Visions for Public Schools in NYC. He has been teaching since 2002, and has worked in Brooklyn, London, Bangkok, and Vancouver before moving back to the United States. He has his Masters degree in Educational Technology from UBC, and is the co-author of a mathematics textbook. He has been published in ISTE's Leading and Learning, Educational Technology Solutions, The Software Developers Journal, The Bangkok Post and Edutopia. He blogs with the Cooperative Catalyst, and is the Assessment group facilitator for Edutopia. He has also helped organize the first Edcamp in Canada, and TEDxKIDS@BC.