Math Forum / Mathematics / Undergraduate Math / July 2009

Hello,

I have to make a simple compound interest calculation:

x = is the amount we pay each month
n = is number of months we pay

now I have to calculate the compound interest at rate r in n months (we calculate it for each month separately).

the simplified formula I wrote for this:

http://www.texify.com/img/%5CLARGE%5C%21%5Csum_%7Bi%3D1%7D%5En%20x%20%2B%20a_%7B
n-1%7D%2Ar.gif

[img]http://www.texify.com/img/%5CLARGE%5C%21%5Csum_%7Bi%3D1%7D%5En%20x%20%2B%20a_%7B
n-1%7D%2Ar.gif[/img]

how can I write the sum above with another formula without sum symbol (to get the equal result with less calculations)? Is that possible?

Thanks a lot for help