Question

A teacher friend of mine lives in Lansing and has to pay the board of water and light for the water that gets used in her household. In December her bill said her household used for CCF (hundred cubic feet) of water in the bill was $28.64. in April her bill said her household you 6CCF in the bill was $34.42.Usually her household uses more water in the summer when she and her husband or not working at school. Explain or show how much she can expect her bill to be if her household uses 9CCF of water in June

Answer 1

She can expect her bill to be of $43.1.

Explanation:

Finding the formula for the price:

The cost is given by a linear equation in the following format:

C(n) = an + b

In which n is the number of CCF, a is the cost per CCF and b is the fixed cost.

In December her bill said her household used for 4CCF (hundred cubic feet) of water in the bill was $28.64.

This means that when n = 4, C = 28.64. So

28.64 = a*4 + b

9a + b = 28.64

b = 28.64 - 4a

In April her bill said her household you 6CCF in the bill was $34.42.

This means that when n = 6, C = 34.42. So

34.42 = a*6 + b

6a + b = 34.42

Since b = 28.64 - 4a

6a + 28.64 - 4a = 34.42

6a - 4a = 34.42 - 28.64

2a = 5.78

a = 2.89

b = 28.64 - 4a = 28.64 - 4*2.89 = 17.08.

The cost of n CCF is:

C(n) = 2.89n + 17.09

Show how much she can expect her bill to be if her household uses 9CCF of water in June

We have to find C when n = 9. So

C(9) = 2.89*9 + 17.09 = 43.1

She can expect her bill to be of $43.1.