How to aggregate percentages

[KriSzy]

Hi All,

i'm back with a math problem in Excel.

The situation:
> one overhead report that aggregates KPI's, i.e. displaying the total sum of the 'slave' reports by adding together corresponding cells to the overhead
> ten 'slave' reports

Complication:
if percentages are entered in the 'slave' reports the aggregated percentage will be a average and not the exact number. For example:

Fractions: 1/4 + 1/6 + 5/10 = 7/20 = 35%
Percentage: 25% + 16% + 50% = 30%

My question to you, is there a cell formula to be created in the overhead report that takes this into consideration. Or have i got it all wrong?

Thankful for any assistance in solving this,

Kristian

 

[RoryA]

Your fractional maths is wrong. You need to get all the fractions with the same denominator:
1/4 = 15/60
1/6 = 10/60
5/10 = 30/60
The average of the numerators 15, 10 and 30 is 18.333. (The average of the denominators is obviously 60) Divide 18.333 by 60 and you get 30.56% just as you do taking an average of the percentages.