AlgebraHardFixed charge from two readings
Algebra practice question
A plumber's total charge is a linear function of the hours worked. A 2-hour job costs $20 and a 6-hour job costs $50. What is the plumber's fixed charge, in dollars, before any hours are worked?
Answer: 5
The rate is 30/4 = 7.50 per hour, so the fixed charge is 20 − 15 = 5.
Common wrong answers
- If you answered 10
- 10 halves the 2-hour cost.
- If you answered 20
- 20 is the 2-hour cost.
- If you answered 7.5
- 7.5 is the hourly rate.
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