# Simple Interest Series

1. ## Simple Interest Series

Hello. I am new to this forum, not entirely sure where to post a question or search to see if the issue has been solved. I tried skimming through several threads, but couldn't find a similar enough problem. Sorry the title is wrong, I messed up the equation.

I am trying to develop a property calculator for an app. It is highly requested by several players, but no one has decided to make one public yet.

The issue I keep encountering is how to calculate the sum of calculation from 1 to n. The math isn't too complicated, but I have no idea how to translate Sigma P+(N*.1P) from 1 to N into excel. I would rather not calculate the this for each of the two dozen properties several thousand times and then find the sum of several thousand cells. I'm looking for a way to compact this into the minimal amount of cells. There will be one cell dedicated to each of the follow: the initial value of the property (P), the change is 10% of the initial property value (.1*P), and the number of properties bought (N), and the total cost (series equation). This of course can be modified if this cannot be accomplished in 4 cells. I am attempting to keep the file size as small as possible to make it easier to download.

A1 = 1000
B1 = 100
C1 = 5000
D1 = Total Cost

Please let me know if I need to clarify anything else. Thank you for taking time out of your day to help solve my problem.

2. ## Re: Simple Interest Series

No-one has helped you yet, possibly because you haven't explained clearly what YOU want. Sigma P+(N*.1P) might mean something to you, but doesn't to me, especially since you didn't say what paparmeter is represented by A1, B1, C1, etc... Can you clearly explain HOW your expected result is to be calculated from your starting point(s).

3. ## Re: Simple Interest Series

The equation is total cost is equal to sigma {series} P+(N-1)RP from 1 to N. P is the initial price of the property.
N is the number of properties bought. R is equal to the increase in price of each property. In this case R is
constant and equal to 10%.

If I want to calculate the sum of buying 5 properties, where P is equal 1000, N is equal 5, and R is equal to 10%,
I would have to find cost of buying each property individual and then find the sum.

Property 1 (N = 1)Cost = 1000 + (1 - 1)*0.10*1000 Cost is equal to 1000.

Property 2 (N = 2)Cost = 1000 + (2 - 1)*0.10*1000 Cost is equal to 1100.

Property 3 (N = 3)Cost = 1000 + (3 - 1)*0.10*1000 Cost is equal to 1200.

Property 4 (N = 4)Cost = 1000 + (4 - 1)*0.10*1000 Cost is equal to 1300.

Property 5 (N = 5)Cost = 1000 + (5 - 1)*0.10*1000 Cost is equal to 1400.

Total Cost = 1000 + 1100 + 1200 + 1300 + 1400 = 6000

That's the extent of the math I understand how to do in Excel. The issue I am running into is the ability to scale
this up to ten or twenty-thousand properties approximately two dozens times (once for each different type of property).
I do not want to have an excel spreadsheet that requires hundreds of thousands of cells to determine the total cost of
buying N number of twenty-four different properties. I tried to use something similar to this,
{=SUMPRODUCT(ROW(INDIRECT("2:"\$A\$1)))}, which I found online. However I kept getting an error. I tried a bunch of
different syntax, but an error kept occurring. I want to condense several thousand of the calculations I did above
into a series from 1 to N. And this series would be using values declared in other cells.

I know how to write a program that will do this, but the interface is more difficult and unfamiliar than an excel spreadsheet.
Several friends of mine in the app expressed concern over downloading a bunch of code they cannot understand, which is
another reason I am trying to do this on excel.

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