Tuesday, July 28, 2015

Modeling - What Algebra Looks Like on the New SAT/PSAT and the Common Core

A bear population, P(t), after t yrs,  is modeled by
P(t)=M-k(t-20)², 0≤t≤20.
Initial population:356
Max pop'n:500
Estimated population after 10 yrs?
Answer: 464
Is this the "new" algebra? Students given a function with PARAMETERS which "models" real world data? Questions like this have appeared on SATs for a few years now and, based on the sample new SAT/PSATs released by the College Board, they will become even more common. Students will be asked to analyze the function and use it in application.
The Common Core also emphasizes algebra models - "using" algebra to solve applied problems.
Middle and secondary math educators are not surprised by any of this as these changes have been around for a while but textbooks may need to include even more examples and homework problems of this type.
The real challenge, IMO, is to find that proverbial BALANCE between traditional algebra skills and  applications.
How much knowledge of quadratic functions is needed for this question? Will most students relate the form of the model to f(x) = a(x-h)²+k? Will they immediately recognize that M must be 500 since (20,500) is the vertex or maximum point? Try it and let me know!
Students should be allowed to explore this function using powerful software like Desmos and Geogebra. Sliders in Desmos allow for considerable analysis when parameters like M and k are given. 
BUT they also need to develop a fundamental knowledge of quadratic functions.
A key question for me is:
Should some background be developed BEFORE exploring with technology or AFTER or something in between?
I included a screenshot from Desmos for the bear population problem but this does NOT show how to IMPLEMENT this powerful tool in the classroom. I'll leave that for the real experts like John Golden! (@mathhombre).

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