David W. answered • 06/30/15
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Part A: For H hours of repair work, the auto mechanic charges:
Labor cost = ($74/hour)*(H hours) (note: hours cancel out, leaving $)
L = 74*H
Part B; The cost of parts was $67 (call that P).
The mechanic charges 74*H + 67 total for labor and parts.
The total charge is $326.
74*H + 67 = 326
74*H = 259 (subtract 67 from both sides)
H = 3.5 (divide both sides by 74; note: 3.5 hours is 3 hours and 30 minutes)
The general equation starts as:
Total T = ($74/hr)*H + P
(T-P) = 74*H (subtract P from both sides)
H = (T-P)/74 (divide both sides by 74; switch sides)
David W.
THX for asking!
No, a time-and-materials service (like car repair) charges for labor per hour plus the purchase price of the parts used (note: they usually throw away old parts, or sell them if they can; they even charge customers a disposal fee for old tires that get replaced). The price of parts is retail, not wholesale, so they make some profit that way.
Now, on a government time-and-materials contract, the company adds the labor costs and the materials costs, then multiplies everything by a profit factor (say, 8%).
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06/30/15
David W.
Oh, sorry, I just re-read my answer and your question.
You are correct about the general formula. The question is somewhat confusing in that it asks for "the amount the auto mechanic charges for H hours of repair work" -- that phrase doesn't mention parts, so I left that out.
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06/30/15
Michael J.
06/30/15