Pam
Posts:
1,507
Registered:
12/6/04


Re: Simplifying Algebraic Expressions with Subtracted Expressions
Posted:
Nov 14, 2013 11:14 PM


> > I guess we would have to ask her, but that she wrote > the solution as just an arithmetic computation makes > me believe that this was a (hard) 5th grade word > problem, rather than an (easy) 7th or 8th grade one. > > Bob Hansen >
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.
Rather ingeniously, in my opinion, Singapore uses the bar diagrams to represent unknowns, quite similar to using letters in algebra but with a useful visual to aid conceptual understanding, making such problems accessible to elementary students. And they are a versatile tool for solving almost any elementary story problem.
Pam

