I hope this question isn't too simple! If it is, let me know if I should post it elsewhere, thank you. (Also, I didn't know what to tag it with, sorry!)
My wife and I live with my brother-in-law Bob, and, for 30% of the time, also live with Bob's three children.
Our last gas bill was for $161.21 for 45 days.
This is how we work Bob's share of the bill. It seems right but I'm sure there are much simpler ways.
Is this correct?
Is there a more efficient way? (I'm sure there is!)
Total cost (a) divided by number of days (b) = cost per day (c)
e.g. $161.21/ 45days = $3.58 per day c = a/b
Then calculate how many days the children were here (30%) (y)
e.g. 30% of 45days = 13.5days y = b/100 X 30
Then calculate how many days the children are not here (z)
e.g. 45 – 13.5 = 31.5 z = b - y
Then find out how much it costs for the amount of days the children are here (d)
e.g. 13.5 x $3.58 = $48.33 d = y X c
Then find out how much per person and times by 4 (Bob + 3 children) (e)
e.g. ($48.33/ 6 = $8.055) x 4 = $32.22 e = (d/6) X 4
Then find out how much Bob owes for the remaining time (f)
e.g. (31.5 x $3.58 = $112.77) / 3 = $37.59 f = (z X c) / 3
Finally, add (e) plus (f):$32.22 + $37.59 = $69.81
x = e + f
x = ((d/6) X 4) + ((z X c) / 3)
x = (((y X c)/6) X 4) + (((b - y) X c) / 3)
x = ((((b/100 X 30) X c)/6) X 4) + (((b - (b/100 X 30)) X c) / 3)
x = ((((b/100 X 30) X (a/b))/6) X 4) + (((b – (b/100 X 30)) X (a/b)) / 3)
Where: a = total cost b = number of days