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I have a very simple question which is bugging me.

We are 3 roommates and our total electricity bill is $61 this month, I was home for the whole month, Friend X was home for 15 days, Friend Y was home for 20 days

now the easy question, how much would each person would pay?

My calculation is 

61/3=20,33 

Guy X : 20,33 / 2 = 10.16
Guy Y : (20,33 * 2) / 3 = 13.55
Me : 61 - (10.16+13.55) = 37.29 which doesn't make sense at all!!!

Help me!!!

George V. Williams
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ufucuk
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2 Answers2

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One way to do it is to think that this month had $$30+15+20=65$$ separate days (or say: electricity days). The electricity bill is $61, and it should be splitted as follows

  1. you should pay $$\$61\cdot \frac{30}{65}=\$28.15$$
  2. friend X should pay $$\$61\cdot \frac{15}{65}=\$14.08$$ and
  3. friend Y should pay $$\$61\cdot \frac{20}{65}=\$18.77$$

Observe now that the 3 amounts sum up to \$61.

Jimmy R.
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  • OMG Such a simple calculation, how come I was not able to think about that, you are the best, thank you! – ufucuk Mar 22 '15 at 18:24
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    There is one thing this calculationdoes not account for (and cannot, without further data): If all three of you were away, certain things like fridge or burglar alarm would still cause a nonzero bill. If this "base" amount wre known, it should be split evenly among all inhabitants and not by Stef's method (though the method kicks in again if you begin/end your tenat contract mid-month ...) – Hagen von Eitzen Mar 22 '15 at 18:28
  • You are welcome. Yes of course that is true (about the other comment). And I assumed that this month had 30 days not 31 (or 28 or 29). So if 31 (or 28 or 29) was the case change 30 everywhere to 31 (or 28 or 29). – Jimmy R. Mar 22 '15 at 18:31
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n = $61/(30.5 + 15 + 20)

30.5 X n = $28.40

15 X n = $13.97

20 X n = $18.63

The individual amounts total $61.