sbryant

That works great. Thanks for the help Shane

I explored seriessum this morning, and I don't think it will do what I am looking for. As I understand it, seriessum requires a hard number or cell references for the coefficients. What I want to be able to do is put in a formula, and the cell return the value (in isolation) without having to reference other cells. I'm not doing a very good job of describing what I'm trying to do Using Sigma notation from Algebra, the problem would have a "k=1" on the underside of the Sigma symbol, 10 (for example) above the sigma, then to the right of the sigma there would be a formula like .85^k. So the answer for this example would be .85^1 + .85^2 + .85^3 + .85^4 + .85^5 + .85^6 + .85^7 + .85^8 + .85^9 + .85^10 = 4.551. What I currently have done in excel is created seperate cells for .85^1, .85^2, .85^3, etc, and add in all the previous values to get a sum for a given value of k (which requires 10 cells in this example). The problem is I want to do, for example, k=1000. To do that, I would have to continue the series above from .85^1 all the way to .85^1000 and get the sum, which would require 1000 cells (or a really long formula within one cell lol). I want to be able to put in the formula for k=1000, and the formula return the total value in isolation without having to total up a bunch of cells (similar to what the website does that I referred to in my previous post). Hopefully that makes sense :/ Maybe I'm not using seriessum correctly? Thanks a bunch, Shane

I'm having a devil of a time figuring out how to do this in Excel. I am trying to put in a formula to calculate a summation where f(x)=.85^k for 1 to k, where k will be a positive integer pulled in from a cell within the spreadsheet. I can manually create a cell for each iteration (k=1,k=2,......), but can't figure out how to use the equation editor to perform the calculation in one step. If I wanted to know the summation when k=1,000, obviously I can't (realistically) create enough cells to calculate that. I found an online calculator here: http://www.math.sc.edu/cgi-bin/sumcgi/calculator.pl that returns an answer in one step, but I want to have multiple "k"s so that I can graph the progression at whatever values I choose, without having a seperate cell for each value of k. For the 1,000 example, you'd enter sigma[1,1000,.85^k] in the box, which returns a value of 5.66 (repeating). Is there a function in Excel (or an add-in) that will do this? Thanks Shane