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They cost peanuts

by Robert Kaplinsky

They cost peanuts

Act One

  • 1.

    Which salted peanuts are the better deal?

  • 2.

    What information would be useful in figuring this out?

  • 3.

    What assumptions are we making?

  • 4.

    What is a guess for which peanuts are a better deal?

Act Two

  • Teacher note
    While the loose peanuts are always going to be cheaper (the loose peanuts are about $0.16/oz vs about $0.18/oz for the bagged peanuts) there are a variety of correct ways to explain how they reached that answer. For example, students could:
    find the cost per ounce of both peanuts
    find the cost per pound of both peanuts
    find out how much 20 oz of the bulk peanuts costs and compare that to the 20 oz bag of peanuts
    The key will be for students to be able “mak[e] plausible arguments that take into account the context from which the data arose.” (Standard for Mathematical Practice 3)
    I have no problem with students using a calculator with this problem. Not only is this a tool we would use in real life and supported by Standard for Mathematical Practice 5, but the sad reality is that if students do not understand the math content, the calculator is not going to help them.


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