
Re: Simplifying Algebraic Expressions with Subtracted Expressions
Posted:
Nov 15, 2013 10:02 AM


Pam says: >Yes, 5th grade, and not particularly hard through the use of the bar diagrams that students studying from the Singapore textbooks are practiced with. They would draw a horizontal rectangular bar, divide it into 5 equal parts, lightly shade 3, divide each of the remaining 2 parts in half (as well as the original 3 so as to continue to have equal portions). By shading 1/4 of the "afternoon tarts" (1/10 of the whole bar), and shading an equal portion of the "morning tarts", what is left of the morning tarts is equal to 200. Since there are 5 parts, each part is equal to 40.
Nice description. I would say that certainly qualifies as "formal manipulation" as in Lou's definition of algebra:
"it's the conscious formal, symbolic representation of an unknown, together with its subsequent manipulation, that turns the solution into an algebraic one." ( Lou Talman)
Cheers, Joe N

