# Math Help - I can't come up with a formula...

1. ## I can't come up with a formula...

The question is...

Residents of the town of Maple Grove who are connected to the municipal water supply are billed a fixed amount yearly plus a charge for each cubic foot of water used. A household using 1000 cubic feet was billed $50, while one using 1600 cubic feet was billed$75.

Some how, I came up with the formula...
C(w) = 24x-200, but it does the opposite of what I want it to do... (you put the amount of dollars in as x instead of the amount of square feet, and it tells you how many square feet the amount of money is worth instead of telling me how much money I would need for x amount of square feet...)

For example...

C(50) = 24(50)-200 = 1000

I need...
C(1000) = formula = 50

I tried inverting it, but it made the problem all funky and didn't work
so I said...

C(w) = w/24+200

I don't know if I inverted it wrong, or if something is just off with my formulas.

2. You simply forgot to divide the 200 by 24 also

C(w) = w/24 + 200/24

3. Ah, I see. I always make those simple errors... Thank you very much