Estimating figures
 

I have four sets of numbers say
100
200
300
400
I also have a set of numbers that correspondes and is multipled to the
number above
1
2
3
4
so it would be
100x1
200x2
300x3
400x4
The total would be 3000

Here is my problem the 100, 200 etc numbers wont change. The 1,2 etc
numbers might but I wouldnt know what to, I would however know that the 3000
total changed to say 3300. If there a formula or a way to figure out what
the different numbers 1,2, etc may have changed too?

I am using round number for this example. In real life the numbers will be
such that chances are there would only be one senioro that would match.

Any help will be appreciated.

Thanks.