Results 1 to 5 of 5

Math Help - numerical skills and prealgebra help:)

  1. #1
    Newbie
    Joined
    Jun 2008
    Posts
    2

    numerical skills and prealgebra help:)

    I have to take a placement test for math for school. The problem is that I haven't done any math in 2 years so my mind is a little rusty. These simple questions are stumping me.

    How do you solve a problem that asks you:

    1) what value of x solves the following proportion?
    9/6=x/8

    I thought the answer would be 11, but it apparently is 12. How do you go about getting the proper answer?

    And also,
    A total of 50 juniors and seniors were given a mathematics test. the 35 juniors attained an average score of 80 while the 15 seniors attained an average/ of 70. what was the average score for all 50 students who took the test?

    I am so lost at how to figure this out.

    any help will be greatly appreciated!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Apr 2005
    Posts
    1,631
    Quote Originally Posted by t.d. View Post
    I have to take a placement test for math for school. The problem is that I haven't done any math in 2 years so my mind is a little rusty. These simple questions are stumping me.

    How do you solve a problem that asks you:

    1) what value of x solves the following proportion?
    9/6=x/8

    I thought the answer would be 11, but it apparently is 12. How do you go about getting the proper answer?

    And also,
    A total of 50 juniors and seniors were given a mathematics test. the 35 juniors attained an average score of 80 while the 15 seniors attained an average/ of 70. what was the average score for all 50 students who took the test?

    I am so lost at how to figure this out.

    any help will be greatly appreciated!
    9/6 = x/8

    There is shotcut which is cross multiplication:
    (numerator1 * denominator2) = (numerator2 *denominator1), meaning,
    9*8 = x*6
    x = 72/6 = 12 -----answer.

    Another way is to clear the fractions. Multiply all fractions by the product of all the denominators:
    (9/6)(6*8) = (x/8)(6*8)
    9*8 = 6*x ----------------same as above.

    - - - - - - - -

    A total of 50 juniors and seniors were given a mathematics test. the 35 juniors attained an average score of 80 while the 15 seniors attained an average/ of 70. what was the average score for all 50 students who took the test?

    Average score for the 50 people here means total score of the 50 people divided by the total number of people---which is 50.

    ...the 35 juniors attained an average score of 80...
    That means each of those 35 juniors got 80....supposedly.

    So, for the 50 people,
    Average score = (35*80 +15*70) / 50 = 77 -----answer.
    Last edited by ticbol; June 30th 2008 at 05:14 PM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member Jonboy's Avatar
    Joined
    May 2007
    From
    South Point
    Posts
    193
    Find x: \frac{9}{6} = \frac{x}{8}
    The left fraction can be simplified as \;\;\frac{3}{2}

    So now you have: \;\;\frac{3}{2} = \frac{x}{8}

    Cross multiply.

    In other words, if you have: \frac{a}{b} = \frac{c}{d}

    Then you do: bc = ad

    So you'll have: 2x = 24 \Rightarrow x = 12
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jun 2008
    Posts
    2
    thanks for the help! I'm slowly starting to get the hang of this again
    Follow Math Help Forum on Facebook and Google+

  5. #5
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Jonboy View Post
    The left fraction can be simplified as \;\;\frac{3}{2}

    So now you have: \;\;\frac{3}{2} = \frac{x}{8}

    Cross multiply.

    In other words, if you have: \frac{a}{b} = \frac{c}{d}

    Then you do: bc = ad

    So you'll have: 2x = 24 \Rightarrow x = 12
    note to the OP. with simple fractions like these, where the variable is just in one location, we can save ourselves at least one step, by doing the opposite operation to what is modifying the variable. example, in this case, we could just multiply both sides by 8, why? because 8 is dividing x

    \frac 32 = \frac x8

    \Rightarrow 8 \cdot \frac 32 = x

    \Rightarrow 12 = x

    be careful when the variable is in the denominator. you can just flip both sides first
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Prealgebra Test
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 14th 2011, 10:42 AM
  2. Prealgebra question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 13th 2009, 10:22 PM
  3. prealgebra help
    Posted in the Algebra Forum
    Replies: 1
    Last Post: October 27th 2009, 08:13 AM
  4. Numerical Methods: Numerical Differentiation
    Posted in the Calculus Forum
    Replies: 0
    Last Post: February 25th 2009, 02:20 AM
  5. communication skills I don't have
    Posted in the Calculus Forum
    Replies: 2
    Last Post: January 5th 2007, 08:03 AM

Search Tags


/mathhelpforum @mathhelpforum