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Homework Help: Solve math problem w/ no algebra

  1. Dec 17, 2009 #1
    1. The problem statement, all variables and given/known data
    Daniel has 7 more stamps than Sherry. Together, they have 101 stamps.
    How many stamps does Daniel have?

    2. Relevant equations
    let x equal how many stamps daniel has

    x - 7 + x = 101
    2 x = 108
    x = 54

    101 - 54 = 47

    3. The attempt at a solution
    Now, we can easily solve this w/ some algebraic equations, but how can we do this without any algebra, or just at an elementary school understanding of math?
     
  2. jcsd
  3. Dec 17, 2009 #2

    gabbagabbahey

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    Homework Helper
    Gold Member

    Trial and error would work fine....why?
     
  4. Dec 17, 2009 #3
    Easy,

    You take the total number of stamps, and take the extra 7 away.

    101-7 = 94

    Now they have an equal number of stamps, so lets split them in half equally.

    94/2 = 47

    Now they each have 47 stamps, but Daniel has 7 more so,

    47 + 7 = 54.

    Stamp count:

    Sherry: 47
    Daniel: 54
     
  5. Dec 18, 2009 #4

    I do understand that you want this to be as comprehensive a possible,
    try not to use x to represent the stamps Daniel has , instead we may use "d" as the student can establish an relationship. And soon they adopt the use of algebra unknowingly. (=
     
  6. Dec 18, 2009 #5
    same suggestion as gabbagabbahey.

    We know Daniel cannot have more than 101 stamps. So assume that he has 50 stamps, Sherry would have 50-7. Total equals 50+50-7 which is less than 101.

    Next assumption 60. Sherry would have 60-7 and total 60+60-7 which is more than 101.

    Next assumption 55....

    This is not trail and error to be honest. It is more like binary search. You keep on reducing the interval like I went from 50 to 60, then 50 to 55, .. then 52.5 to 55
     
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