Results 1 to 4 of 4

Math Help - Averaging problem?

  1. #1
    Newbie
    Joined
    May 2010
    Posts
    13

    Averaging problem?

    This is yet another problem on the sample 7th grade EOG test.

    Shana and Mina are workign on a math project and will receive the same grade. Their individual grades before the project are listed below.



    What grade could they receive that will keep Shana's average the same, but improve Mina's average by one point?

    A) 83
    B) 85
    C) 87
    D) 90

    I worked this problem last night and I got D) 90, but I had to go thru all the possible answers before I got to the right answer. My question is, is there any short cut, or this the only way to solve a problem like this?
    Last edited by cherryperry; May 29th 2010 at 01:38 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    Quote Originally Posted by cherryperry View Post
    This is yet another problem on the sample 7th grade EOG test.

    Shana and Mina are workign on a math project and will receive the same grade. Their individual grades before the project are listed below.



    What grade could they receive that will keep Shana's average the same, but improve Mina's average by one point?

    A) 83
    B) 85
    C) 87
    D) 90

    I worked this problem last night and I got D) 90, but I had to go thru all the possible answers before I got to the right answer. My question is, is there any short cut, or this the only way to solve a problem like this?

    _________________

    I also have another problem that's similar, but I'm unable to figure it out:

    Charlie and Daniel are playing darts. The winner will be the one wtih the highest average score after 6 games. Charlie ahs completed 6 games and has an average score of 190. So far, Daniel has played 5 games and has an average score of 183. What score does Daniel need in his final game to have the same average score as Charlie?

    A) 190 points
    B) 197 points
    C) 225 points
    D) 270 points

    How do I begin to tackle this? I figure it's got to be simple b/c it's on a 7th grade test. I think?
    Hi Cherry,

    yes, there is a fast way to get the first one.

    Calculate Shana's average, which is 450/5=90

    In order to keep her average the same, she needs a 90
    as below 90 will drop her average and above 90 will raise it.

    Apparently that will necessarily raise Mina's average by 1,
    so that information was in fact irrelevant as only 90 will keep Shana's average steady.

    For 2) you need \frac{183(5)+x}{6}=190
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2010
    Posts
    13
    Thanks, Archie! Wow, that sure does simply things!

    Can you tell me how to go about solving this one?

    Charlie and Daniel are playing darts. The winner will be the one withh the highest average score after 6 games. Charlie has completed 6 games and has an average score of 190. So far, Daniel has played 5 games and has an average score of 183. What score does Daniel need in his final game to have the same average score as Charlie?

    A) 190 points
    B) 197 points
    C) 225 points
    D) 270 points

    How do I begin to tackle this?

    Edited to correct spelling.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    Quote Originally Posted by cherryperry View Post
    Thanks, Archie! Wow, that sure does simply things!

    Can you tell me how to go about solving this one?

    Charlie and Daniel are playing darts. The winner will be the one withh the highest average score after 6 games. Charlie has completed 6 games and has an average score of 190. So far, Daniel has played 5 games and has an average score of 183. What score does Daniel need in his final game to have the same average score as Charlie?

    A) 190 points
    B) 197 points
    C) 225 points
    D) 270 points

    How do I begin to tackle this?

    Edited to correct spelling.
    Yes,

    Daniel's average of 183 is his first 5 scores added together and divided by 5.
    Therefore the sum of his first 5 scores is 5(183).

    The average of his entire 6 scores will be the sum of the first 5 plus his final score.
    We can call the final score x.

    Then, after 6 rounds his average is

    \frac{sum\ of\ 6\ scores}{6}=\frac{sum\ of\ first\ 5\ scores+final\ score}{6}=\frac{5(183)+x}{6}

    and this needs to be 190

    \frac{5(183)+x}{6}=190

    5(183)+x=6(190)

    915+x=1140

    x=1140-915
    Last edited by Archie Meade; May 30th 2010 at 02:06 AM. Reason: small typo
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Averaging Digit...
    Posted in the Number Theory Forum
    Replies: 3
    Last Post: November 5th 2009, 05:38 PM
  2. Averaging Question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: October 31st 2008, 02:51 AM
  3. Averaging a matrix
    Posted in the Business Math Forum
    Replies: 2
    Last Post: October 13th 2008, 10:25 AM
  4. Averaging discrete variables
    Posted in the Advanced Statistics Forum
    Replies: 6
    Last Post: August 19th 2008, 06:19 AM
  5. Probability averaging?
    Posted in the Statistics Forum
    Replies: 6
    Last Post: January 13th 2008, 09:24 PM

Search Tags


/mathhelpforum @mathhelpforum