the cost for using 20 HCF of water is $47.36
Step-by-step explanation:
Linear function is in the form: y = mx + c
Let the monthly cost (in dollars) of water = y
the amount of water used (in hundreds of cubic feet, HCF) = x
when y = $38.46, x =14 HCF
Inserting in the equation of line:
38.46 = 14m + c ...equation 1
when y = $73.26, x = 38 HCF
73.26 = 38m + c ...equation 1
To get m = slope = change in y/ change in x
(x, y) = (14, 38.46) and (38, 73.26)
m = (73.26-38.46)/(38-14)
m = 34.8/24
m = 1.45
Insert the value of m in any of the equation to get intercept (c):
using 73.26 = 38m + c
73.26 = 38(1.45) + c
c = 73.46 - 55.1
c = 18.36
The equation of the function becomes: y = 1.45x + 18.36
To get the cost for using 20 HCF of water, we will use the equation:
y = 1.45x + 18.36
x = 20HCF, y = ?
y = 1.45(20) + 18.36
y = 29+18.36
y = 47.36
Therefore, the cost for using 20 HCF of water is $47.36