Sum function with formula

[pernille]

Hello experts,

Is it possible to sum a formula like below in an excel cell (and how?):

for i=0 to m-1 Sum ((m-i)/m * x)

where 1<m=<12.

In my sheet I wish to do the calculation for a lot of rows a m and x value for each row.

Hope you can help me with this challenge.

Thanks!!

 

[wideboydixon]

So this is SUM(1 to m)/m * x

SUM(1 to m) = m * (m + 1) / 2
SUM(1 to m) / m = (m + 1) / 2
SUM(1 to m) / m * x = x * (m + 1) / 2

You can run a complex formula to do the iteration but in the end there's a simple answer:

Book1
	A	B	C	D
1	m	x	complex answer	easier
2	10	5	27.5	27.5
3	5	1	3	3
4	20	6	63	63
5	7	7	28	28
Sheet2

Cell Formulas
Range	Formula
D2	=$B2*($A2+1)/2
C2	{=SUM(($A2+1-ROW(INDIRECT("A1:A"&$A2)))/$A2*$B2)}
Press CTRL+SHIFT+ENTER to enter array formulas.

WBD