Sumproduct formula question

Hi all,

lets say i have 5 known integers:

5000, 6000, 7000, 8000 and 10000.

Some have corresponding percentage values (lets say the first 4 in this case):

70%, 72%, 74%, 85%

What would a formula look like, that would calculate the needed % for the last value (10.000) in order to achieve a weighted average of x% (80% in this case).

I'll try to attach a file asap

Book3.xlsx

Hi Punnam,

thanks for the Forecast formula! Didn't know that one exists

I'm afraid that this isn't what I was looking for - It's my fault by all means: I didn't make myself clear.

The formula in the blue cells has to return a number with which the actual% (red cells) shows exactly the needed %. In the first case, it was close by accident - if I'd change the 10.000 to 20.000 the value is much bigger. The Cell F3 has to equal 90.000198% in order to achieve exactly 80.00% - thats the number which the formula has to evaluate to :/