Question 630083: The monthly cost (in dollars) of water use (in dollars) is a linear function of the amount of water used (in hundreds of cubic feet, HCF). The cost for using 16 HCF of water is 37.69, and the cost for using 29 HCF is 57.84 . What is the cost for using 27 HCF of water?
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! The monthly cost (in dollars) of water use (in dollars) is a linear function of the amount of water used (in hundreds of cubic feet, HCF). The cost for using 16 HCF of water is 37.69, and the cost for using 29 HCF is 57.84 . What is the cost for using 27 HCF of water?
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The form of an equation for a linear function like a straight line: y=mx+b, m=slope, b=y-intercept
For given problem:
y=cost of using 27 HCF water
let x=amt of water used
m=∆y/∆x=(57.84-37.69)/(29-16)≈1.55 ($/HCF)
equation: y=1.55x+b
solving for b using point (16,37.69)
37.69=1.55*16+b
37.69=24.8+b
b=37.69-24.8
b=12.89
equation:
f(x)=1.55x+12.89
f(27)=1.55*27+12.89
=54.74
cost of using 27 HCF water=$54.74
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