Mixture Problems

[shelahf]

In 8th grade, mixture problems were specifically notated in the ’97 standards yet in Common Core it isn’t mentioned. I have referenced the EE Progressions and Illustrative tasks as for a clue as to its appropriateness in 8th grade content and I’m not finding any answers. Do you feel that traditional mixture problems are appropriate for 8.EE.8.A and how much time should be spent on that concept?

[Bill McCallum]

Mixture problems are certainly among the problems you might give students in Grade 8 working with simultaneous equations. But I think you have be clear in your own mind what the purpose of doing so is. If mixture problems occur among a range of problems where students have to model a situation by setting up a system of simultaneous equations, solve the system, and then interpret their solution, then that’s good. If the idea is to have a separate unit called “mixture problems” where you look at a lot of problems following a fixed template, and train students in a fixed procedure for dealing with that template, then that’s bad. It’s not the type of problem that is important, but learning flexible skills and understandings that can be applied to other types of problems with the same structure that are not about mixtures.

[Author]

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