Weighted average of %

[drluke]

I need to do a allocation of time spent with customers using weighted averages

I have 10 customers with a % of total of all time spent for each (I don't know the total of all time).

I spend 50% of my time with Customer A004. I need to allocate the remaining 50% of my time to the remaining customers using a weighted average of the % of total time spent, as shown in the table below. Is there a formula I can use to perform this calculation.
[TABLE="class: grid, width: 300"]
<tbody>[TR]
[TD]CUSTOMER[/TD]
[TD]% Time[/TD]
[/TR]
[TR]
[TD]A001[/TD]
[TD]27%[/TD]
[/TR]
[TR]
[TD]A002[/TD]
[TD]15%[/TD]
[/TR]
[TR]
[TD]A003[/TD]
[TD]3%[/TD]
[/TR]
[TR]
[TD]A004[/TD]
[TD]8%[/TD]
[/TR]
[TR]
[TD]A005[/TD]
[TD]1%[/TD]
[/TR]
[TR]
[TD]A006[/TD]
[TD]4%[/TD]
[/TR]
[TR]
[TD]A007[/TD]
[TD]2%[/TD]
[/TR]
[TR]
[TD]A008[/TD]
[TD]18%[/TD]
[/TR]
[TR]
[TD]A009[/TD]
[TD]12%[/TD]
[/TR]
[TR]
[TD]A010[/TD]
[TD]10%[/TD]
[/TR]
[TR]
[TD]TOTAL TIME[/TD]
[TD]100[/TD]
[/TR]
</tbody>[/TABLE]

 

[sgroath]

If A001 is cell A2, then C2 should be:
=B2*(1-0.5)/(1-SUMIF(A$2:A$11,"A004",B$2:B$11))

Copy that formula down through C11 and delete it fir cell C5 and you will have your percentages to allocate.