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Homework Help: Solution to simple math problem again . . .

  1. Dec 14, 2009 #1
    1. The problem statement, all variables and given/known data
    Laura has $1.50 in dimes and nickels. She has twice as many dimes as
    nickels. How many dimes does she have?

    3. The attempt at a solution
    12 dimes and 6 nickels, duh.

    The actual question is, how would I explain this to an elementary school child who has never had any experience with systems of equations? (the way I did it)
     
  2. jcsd
  3. Dec 14, 2009 #2

    Mark44

    Staff: Mentor

    Start with variables that represent the number of each type of coin.

    Let d = the number of dimes
    Let n = the number of dimes.

    Now translate the first and second sentences into two equations, keeping in mind that the value of a dime is 10 cents and the value of a nickel is 5 cents. (It's probably easier to write the total value as 150 cents rather than 1.5 dollars.)
     
  4. Dec 14, 2009 #3
    Not sure what level of elementry school you mean, but this might work.

    Do it case wise...
    The number of dimes dictates the number of nickels.

    Start with the most simple case...

    1 nickel 2 dimes = $0.25

    To small, so go bigger.

    100 nickels, 200 dimes = $25

    Too big.

    There must be something in the middle...

    Then pick someting you know is close to the answer.

    10 dimes, 5 nickels = $1.50

    Eventually work up or down to the answer.

    However, if you're doing algrbra, try doing the system of equations.
     
  5. Dec 15, 2009 #4

    Mark44

    Staff: Mentor

    flatmaster, your approach might be better than mine. I saw the part about explaining to a kid in elementary school, but it didn't really click with me.
     
  6. Dec 15, 2009 #5
    Use model to relate to algebraic system.
    It always work
     
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