Excel: Summation formula, from a value in a cell, to a value in another cell

Question

I have the following summation formula :

In text:

SUM (k*1.07^n), n=c1 to n=c2

k , c1 and c2 are 3 single numbers, specified in respective individual cells.

k is a constant, but c1 and c2 should be dynamically changeable.

Is that possible to do in Excel, and if so, how?

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I know it's a fairly simple mathematical concept so I'd be surprised if Excel couldn't do it, but I haven't been able to find the formula myself. I've tried SUM and SUMIF , but from what I understand, that requires me to fill a whole range of cells each time I want to calculate something. I've also found some suggestions to use arrays in Excel, which I understand is automatically filling cells - which is at least a little more automated - but I'd rather not fill extra cells, if it's possible.

As a sidenote, I read Excel's accuracy is bad in high digit numbers, but as long as the first 5 digits are correct, it'll be accurate enough for my purpose.

Answer 1

With k , c ₁ , and c ₂ in A1, B1 and C1 respectively, use the following formula:

=A1*SUMPRODUCT(1.07^ROW(INDIRECT(B1&":"&C1)))

Regards