
Re: Simplifying Algebraic Expressions with Subtracted Expressions
Posted:
Nov 15, 2013 3:11 PM


On Nov 15, 2013, at 2:42 PM, Joe Niederberger <niederberger@comcast.net> wrote:
> R Hansen says: >> What she did was reverse engineer the solution *she* already knew. > > She reverse engineered it from the number 400? I doubt it. I wasn't there, but I think a more likely guess is that the hypothetical kid *knew* the process, the steps, of how to get an answer this way. > > Cheers, > Joe N
No, not from just the numerical result, from the arithmetic of the solution. You can't fabricate the blocks in the right quantities, multiples, etc. and have it all tie out and lead to the result unless you already know the arithmetic of the solution, the fractions, the common denominators, etc. But if you know all that, then you have already solved the problem. I can take any solved problem and turn it into a clever visualization. Try it yourself if you don't believe me. Now try it with an unsolved problem. Pick some decent problem at random from some textbook and try to solve it in this manner without already solving it rationally.
It's a cruel parlor trick played out on students and parents that don't know any better. An evasion.
Sorry
Bob Hansen
PS: The *process* is mathematical reasoning, not drawing.

