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Calculate the required % Rate increase amount to obtain a goal

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    Exclamation Calculate the required % Rate increase amount to obtain a goal

    This is something I can easily do with Goal Seek...however, I need to do that with a Table with 1,000 rows...plus each row has to be calculated independently, and then the Total Row will also have to be calculated. And of course there are many different ways the Table could be filtered, and the Total Row has to dynamically change regardless of how the Table is filtered.

    If I could have a Formula that worked like Goal Seek, that would be optimal...and I don't want to write code to do it.. (Although I will if I can't figure this out...)

    Here's the easiest way I can describe it...but it's one of the questions where if you ask "why" it will take a lot longer to explain. Just accept the scenario.

    * Assume a checking account has a balance of $25,000 today
    * Assume I will make a deposit monthly into the account.
    * The account does not earn any interest; this is not a rate-of-return question.
    * The first deposit is for $1,000.
    * the 2nd Deposit is increased by 5%, or $1,050
    * the 3rd Deposit is increased another 5%, or $1,103
    * the 4rd Deposit is increased another 5%, or $1,158
    etc
    etc
    etc
    * the final deposit, the 12th one, is for $1,720.
    * total amount of the 12 deposits was $15,917 and now my checking account balance is $40,917.


    In that case, I provided the 5% growth rate, and calculated the ending bank balance. My case is where I want provide a "desired" bank balance, and Excel figures out the growth rate I need.
    - For example, if I want my bank balance to be $42,000 at the end of 12 months, how much does each deposit need to increase?
    - using Goal Seek, I can figure out the value is 6.131%.

    There should be a simple file attached to this post, I hope...

    How can I do that using my table of 1000 rows? Each row will have a different Initial Deposit value and a different Desired bank balance, and therefore a different Growth rate.
    Attached Files Attached Files

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    Re: Calculate the required % Rate increase amount to obtain a goal

    I know you claim that this is not a rate of return question, but the math sure seems similar to a present value/future value/compound interest problem. Some observations leading up to the solution:

    1) in D8 and down, I enter the deposit numbers -1 -- 0,1,2,3...11
    2) In G8, I enter =FV($C$6,D8,0,$C$4) and copy down to G19. All values match those in column C, so it looks like the FV() function is related to the problem.
    3) In H8, I enter =FV($C$6,D8,$C$4,$C$4) and copy down to H19. H19 contains the same value as C20.
    4) If I put =C22-C5 into a cell (G22), then put =RATE(D19,-$C$4,-$C$4,G22), I get the 5% matching the value in C6.

    So, it appears to me that we can use the present value/future value family of functions to model this scenario, and use the RATE() function to compute the desired growth rate. So, for example 2, I:
    5) Enter =C29-C28 in a cell (D29).
    6) Calculate the rate using the RATE() function in E29 =RATE(11,-C27,-C27,D29). I get 6.13% to match the goal seek value in C31.
    Quote Originally Posted by shg
    Mathematics is the native language of the natural world. Just trying to become literate.

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    Red face Re: Calculate the required % Rate increase amount to obtain a goal

    MrShorty - Thank you! I tried using the Rate() function but could not ever get what I needed; i kept using the Starting Bank Balance as a PV, and the desired ending balance as the FV with many variations, but never achieved the correct answer.

    It didn't occur to me to to use (Ending Balance - Starting Balance) as the FV, and to use the Initial Deposit as both the PMT and PV.

    You've helped me quite a bit, I thank you!

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