I'm trying to make a spreadsheet to split the house bills with my SO.
I want to split the bills accordingly to our income so (the values are dummy)
incomeA = 1000;
incomeB = 600;
percA = incomeA / (incomeA + incomeB); (0.625)
percB = incomeB / (incomeA + incomeB); (0.375)
This is "our 50/50" and, in most of the bills is ok. If we have a bill of 40, I will play 25 (40 * 0.625) and she will pay 15 (40 * 0.375).
Now, let's say that we have a bill that I want to pay more than the "our 50/50" (75/25, for example) How can I translate our 50/50 ratio into that 75/25?
I don't really know how to put this in better words. Thanks in advance
For a simple solution, we set a multiplier (say $\lambda_1$) to incomeA and another one (say $\lambda_2$) to incomeB, in a way that $\lambda_1+\lambda_2=1$ (or $100$ if it results more intuitive).
In the case of the 75/25 ratio you mention in your example, we would set
$$\text{incomeA} = 1000*\lambda_1=1000*0.75$$ $$\text{incomeB} = 600*\lambda_2=600*0.25$$
We would do the same for the 50/50 example, with $\lambda_1=\lambda_2=0.5$.
The true amounts of incomeA and incomeB do not really matter since we are mostly interested in getting the percentages percA and percB.