SOLUTION: A plumber charged $110 for a three-hour job and $160 for a five-hour job. At this rate, how much would he charge for an eight-hour job? Assume that this situation can be described

Question 198019This question is from textbook Algebra and trigonometry
: A plumber charged $110 for a three-hour job and $160 for a five-hour job. At this rate, how much would he charge for an eight-hour job?
Assume that this situation can be described by a linear function. This question is from textbook Algebra and trigonometry

Found 2 solutions by Alan3354, josmiceli:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A plumber charged $110 for a three-hour job and $160 for a five-hour job. At this rate, how much would he charge for an eight-hour job?
Assume that this situation can be described by a linear function.
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The difference in charges is $50 for a difference of 2 hours, so the hourly rate is $25.
The overall charge is some base price, plust $25/hour.
$110 = b + $25*3
b = $35
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For 8 hours, charges = $35 + $25*8
= $235
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PS This must be an old math book - plumbers charge a LOT more than that.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
If I plot time on the horizontal and the charge on the vertical,
linear means that a straight line goes through the points
(3,110) and (5,160)
Let = elapsed time in hours
Let = charge in dollars
The formula to use is:

Multiply both sides by

Now plug in

He charges $235 for an 8 hr job
I'll plot the line:

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