Algebraic Expressions vs Algebraic Equations

Give the algebraic expression that represents the perimeter of the following polygon. 
001 Perimeter Diagram

Over the last five years working as a tutor I have seen many students struggle with a problem like the one above. To answer it we must remember that the perimeter of any shape can be found by adding up its side-lengths. With side-lengths that are numbers this is straightforward, but with side-lengths that have variables and numbers it can be tricky—you need to know how to identify like-terms and how to sum them correctly.

001 Perimeter Expression

Therefore, the perimeter of the polygon is 13x-34 units.

But getting an answer such as 13x-34 is not necessarily what students have in mind as an answer. Often, they expect and, perhaps, want a number. Continue reading “Algebraic Expressions vs Algebraic Equations”