I have a computer program that finds the arithmetic mean of 9 numbers. Sometimes, though, it needs to eliminate some of those numbers from consideration - in other words I actually need it to actually find the average of a set of 1-8 numbers that is a subset of those 9.
It'd make my program significantly slower and more complicated to have it notice that it needs to do so and adjust the summing and dividing accordingly; it'd be better to have it always sum 9 numbers and divide by 9.
This is kind of a long shot, but I thought I'd ask: is there any simple way to take that average and "remove" one of the numbers from it, or is there a value such that if N of the 9 values is that value then the average of the set will equal the average of the set minus those numbers?