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Math help requested

Locust76Locust76 Registered User regular
I thought I'd ask here since I can't seem to wrap my head around how to do this. I'm going through a divorce and attempting to get support payments and whatnot set up in such a way that they are fair.

Basically I need help figuring out a formula where I can take a single fixed payment (€220 in this case, but I will apply it to other payments) and divide it up in such a way that we both contribute proportionally the same.

My ex wife has an income that's 56% of my own. I can't just use the percentage here, because proportionally 44% of 220 is a lot more of her income than it would be of mine, know what I mean? Somehow it has to be calculated using a ratio and not a percentage, and I was too bad in math at school to figure shit out like this.


  • CauldCauld Registered User regular
    If I understand what you're trying to do correctly, you should divide the individual incomes by the combined income to get the proportion each person should pay. So if her income was 560 and yours was 1000, the denominator would be 1560.

    560/1560*220 = ~79
    1000/1560*220 = ~141

  • khainkhain Registered User regular
    edited October 2016
    Initial: (Y here is how much you would pay)
    Total = 0.56 * Y + Y
    Converting for how much she would pay:
    Her = Total * (0.56 / 1.56)

    You can't use 44% as 56% is the proportion of her salary to yours, not her salary to the total. The proportion of her salary to the total is instead 56% / 156% or about 35.9%. If it makes it easier to conceptualize, the 0.56 / 1.56 is ratio of her income over the total income between the two of you and could be replaced with that ($560 / $1560 using Cauld's numbers).

    khain on
  • Locust76Locust76 Registered User regular
    Friggin' awesome. Thanks guys, that's exactly what I needed! I plugged that formula into my excel sheet and came up with two payments of roughly 8.68% of our incomes each. That will make splitting such future costs very simple and fair.

    Thanks again!

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