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Math Problem: Working Backwards Algebraically

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    Math Problem: Working Backwards Algebraically

    Hi All,

    I am attaching a worksheet here, it is more a math problem than excel problem but have been scratching my head over how to work backwards.

    If you can kindly see attached.
    Attached Files Attached Files
    Last edited by AliGW; 09-28-2018 at 03:22 AM.

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    Re: Math Problem

    Hi Everyone,

    I am trying to work backwards algebraically on a problem here. I have attached the file as it explains better than I can in words.

    I basically have a sort of pipeline where I go through different stages of wins and cancellations.

    For example: I start with a value of 100 and if I win approx 20% then the following value will be 100*20% = 20, from this 20 it then goes through stages of cancellation i.e. 20% cancellation = 20 * (1-20%) = 16

    I have written the equation going forwards but I am having some trouble moving backwards, seems my algebra is not up to par.

    Any help would be really appreciated.

    Please see the file as it would be easier to see it mathematically than just through my simple example above.

    Thank you very much in advance

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    Administrator FDibbins's Avatar
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    Re: Math Problem

    First, let me begin by apologizing for what, Im sure, feels like you are being ganged up on by mods and admin. That was most certainly NOT the intention, and Im sorry if it came across that way

    Second, there really was no reason to send a sarcastic message to one of my mods, I would expect an apology from you to them.

    Third, I can see how you would have a hard time finding a suitable heading for this. For now, Im going to allow the heading to remain as is, and, moving forward on this thread, we can see if we can come up with something better.
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    Forum Moderator AliGW's Avatar
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    Re: Math Problem

    The title used in the closed duplicate was better. I have amended accordingly.
    Ali


    Enthusiastic self-taught user of MS Excel who's always learning!
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    Re: Math Problem: Working Backwards Algebraically

    Thanks Ali

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    Re: Math Problem: Working Backwards Algebraically

    I looked at this yesterday and hadn't much of a clue about what was going on. I looked again today and am still confused....

    If 40 (G5) is being split 80:20 between B and C... 32 should appear in B (and it does - in J5) and B in C (but 44.4 does - in N5). Can you please EXPLAIN what you are trying to do and ensure that the column headers are correct (and understandable - what on earth in B CXL % meant to mean)?
    Glenn




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    Re: Math Problem: Working Backwards Algebraically

    Hi Everyone,

    Thanks and many apologies. And for the file itself apologies if it is hard to read. I am attaching a version that is much more detailed. If this is still confusing please let me know and I will try to explain further.
    Attached Files Attached Files

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    Re: Math Problem: Working Backwards Algebraically

    When I opened the file cell S5 was displaying 91.55...
    The formula for that cell (=R5+Q4) suggested that it should be showing 77.96 (57.96 + 20)
    91.55... was also displayed in cell U10 as a result of 90.64/.99
    However after enabling editing the values in S5 and U10 changed to 77.96 so that the value in cell S10 became 57.96 which matches the value in R5 as I believe you are expecting. Perhaps at some time when you were working with the spreadsheet the calculation mode was switched from automatic. I'd suggest checking that in the options.
    As bit of an FYI here I think that you may be able to use Excel's Goal Seek to avoid the reverse math.
    Select cell AA5 then select Goal Seek (Data tab under What if Analysis)
    Type your desired end value in the 'To Vaule' window
    Type C5 in the 'By changing cell' window
    Press OK
    Let us know if you have any questions.
    Consider taking the time to add to the reputation of everybody that has taken the time to respond to your query.

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