Results 1 to 3 of 3

Math Help - Percentage problem

  1. #1
    Newbie
    Joined
    Oct 2010
    Posts
    2

    Percentage problem

    Hey guys, this my first post here and I hope that there is someone that can help me with a problem that I came across. I'll try to explain

    Basically I haveis one table with two rows. At one point of the table I have percentage P1 of sums of all previous values of x and y rows. At some other point I have second percentage P2, but also I know the values of x and y which made percentage increase... The problem here is to find what is the value of 1% at second point.

    If we say that Sx is sum of x row, and Sy sum of y row, that percentage at some point is P=Sx/(Sx+Sy)... Just so you know what percentage am I talking about

    Here is a picture of a table:

    I hope that someone could help me with this one I guess that I just get lost somewhere in my calculations
    Thanks...
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,540
    Thanks
    780
    Hi,

    It's curious that you use the word "row" to mean "column" and "point" to mean "row"...

    Please tell us if the following rephrasing is correct. You have two sequences of numbers: x_1,\dots,x_n and y_1,\dots,y_n. Also, there is a number k < n. Let X_k=x_1+\dots+x_k, Y_k=y_1+\dots+y_k, X_n=x_1+\dots+x_n, Y_n=y_1+\dots+y_n. Also, let P_1=X_k/(X_k+Y_k) and P_2=X_n/(X_n+Y_n). Do you need to find X_n+Y_n, or 0.01(X_n+Y_n) in the end?

    If so, let X=X_n-X_k and Y=Y_n-Y_k. Then you have two equations:

    X_k/(X_k+Y_k)=P_1
    (X_k+X)/(X_k+X+Y_k+Y)=P_2

    with two unknowns X_k and Y_k, so the equations can be solved.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2010
    Posts
    2
    Hi emakarov, thanks for your answer I'm sorry for swapping row and column, about the point, I meant as a point in the time, since values are added every few seconds, as table changes all the time... Just that wasn't the issue so I didn't mentioned it

    About the solution, funny thing is that I solved it 15mins ago... I guess that sometimes is a good thing to take a break You are right about the problem, and you described it very good... My solution went in a bit different way, but end result is the same, so thank you very much...

    Oh, and sorry if my English is not perfect, it's not my native language

    Thank you very much again...
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: August 26th 2011, 09:19 PM
  2. Percentage problem
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 2nd 2009, 01:33 PM
  3. Need help with a percentage problem
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 30th 2009, 03:09 PM
  4. Percentage problem
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 3rd 2009, 05:16 PM
  5. Percentage problem
    Posted in the Algebra Forum
    Replies: 4
    Last Post: July 29th 2009, 04:15 PM

/mathhelpforum @mathhelpforum