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COTR Quiz 7.4-7.5

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    COTR Quiz 7.4-7.5

    We are still finishing Pre Algebra. For #5 of this quiz the answer should be $6000.
    Courtney
    Mom to 5 boys-14,13,10,8,5 and the girls- 3 and 1

    #2
    Re: COTR Quiz 7.4-7.5

    Originally posted by Courtney View Post
    We are still finishing Pre Algebra. For #5 of this quiz the answer should be $6000.
    Good morning,

    Hmm, it looks like the issue here is rounding. If we round (.085)(2/12) down to .0141 we get the (rounded) answer in the Key: $6028. If we round up to .0142 then we get $5986 (again, rounded). However, if we use a calculator to complete all of the operations in one step, not rounding until the end, then we get an even $6000. Now, that is as far as my math abilities go, so hopefully Cindy will chime in on which answer she would expect from a student.

    HTH (at least temporarily)!
    Michael
    Memoria Press

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      #3
      Re: COTR Quiz 7.4-7.5

      Thanks. The question was answered in number 17 of Lesson 7.5. You multiply both sides by 6 instead of multiplying (0.085)(1/6) first. I did the same thing Micheal because of the way it is shown in the quiz key until I looked in the solutions manual.
      Courtney
      Mom to 5 boys-14,13,10,8,5 and the girls- 3 and 1

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        #4
        Re: COTR Quiz 7.4-7.5

        Originally posted by Courtney View Post
        Thanks. The question was answered in number 17 of Lesson 7.5. You multiply both sides by 6 instead of multiplying (0.085)(1/6) first. I did the same thing Micheal because of the way it is shown in the quiz key until I looked in the solutions manual.
        Courtney has determined the correct answer, $6,000.

        I don't have the solutions guide at home, but here is my solution to the problem (difficult to type in text format, but hopefully it will make sense).

        Equation for simple interest: I = prt
        Solve for p: p = I/rt
        Convert interest rate to decimal form: 8.5% = .085
        Since the interest rate is annual, divide 0.085/12 to get monthly equivalent, r, but don't do the division yet. Leave in integer form.
        t = 2months (given)
        I = $85 (given)
        substituting: p = 85/[(0.085/12)*2]
        simplify the denominator: p = 85/(0.085/6)
        multiply by reciprocal of the denominator to complete the division: p = 6*85/0.085
        simplify: p = 6*1000 = $6,000

        Hope this helps! (Sounds like the answer key needs to be corrected.)
        Cindy Davis
        Science and Math teacher at Highlands Latin School - Indianapolis
        ds-24 college graduate: working, reading, writing
        ds-23 college graduate: 1st year med school
        dd-21 college junior: Nursing

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