The Hydro water department has a monthly service charge of $13.90 and a volume charge of $1.45 for every 100 cubic feet of water
. The total monthly cost is equal to the service charge plus the charge for the volume used during the month. If we let x represent the number of cubic feet of water (in hundreds) and y represent the total monthly cost, then we have:
total monthly cost = volume charge + service charge
y = 1.45x + 13.90
If the Johnson family used 200 ft3 more water this month than last month, then they can expect
A. an increase in their water bill of $2.90.
In this question, you can disregard the initial $13.90 cost because we're only looking for an INCREASE in price. If the Johnson family used 200 cubic feet MORE of water, we need to multiply 2 * 1.45 which gets us 2.90. We multiply 2 by 1.45 because 200 represented in x is 2, since x is represented in hundreds.
This is a unit rate problem. If we want to find out how much chocolate was eaten in 1 minute, we divide 31.5 by 7. This gives us the number of ounces of chocolate eaten in 1 minute: 4.5 ounces per minute.
