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Homework Help: Your opinion on how to interpret a problem

  1. Oct 24, 2011 #1
    I'm grading some homework (I'm a TA) and one of the word problems is rather vague. The problem is very short, it asks one to calculate a property of two objects, and then asks "how much more" for one of the objects.

    When I took the class I considered this as asking for the difference between quantity A and B. The TA when I took the class end up taking off 40% of what the problem was worth. The correct answer was to calculate a ratio. The wording, in my opinion, was too vague, and for me, when someone asks "how much more" one object is with regard to another, that's asking for a difference of some sort.

    Now that I'm in the TA position, I don't necessarily want to punish people for interpreting problem like I originally did. I'm going to give full credit for anyone that calculated a the difference correctly regardless of what anyone posts here. Indeed, by the time anyone replies the homework will be graded and out of my hands.

    So, just curious, how would any of you handle this?
  2. jcsd
  3. Oct 24, 2011 #2
    IMO it seems vague to me as well. I would do what you plan to do unless specific instruction was given in class.
  4. Oct 24, 2011 #3


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    Homework Helper

    Your original description of the problem did not refer to the word difference [which implies subtraction].
    Expressing an increase as a factor or percentage increase is by far the most common.

    For example, suppose you have a wire of given resistance, then another is made from wire whose resistivity is 0.1 more, it is 1 metre longer and 0.5 mm thicker. What will be the resistance of the new wire?

    Where as if the resistivity is 130% greater, it is 12.5% longer and 20% thicker .....

    As a stand alone queston, there may be some ambiguity, but in the context of the other questions involved, the type of answer should be obvious. If I were a student, I would be saying "that's an increase of 47.5 or 12%" to cover both bases.

    EDIT: I would be interested in seeing the exact wording of the question you refer to.
  5. Oct 24, 2011 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper

    I would consult with the course professor, and explain your reasoning. It might be best to accept either form of answer.
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