AlgebraHardBoat hire cost from two known prices
Algebra practice question
The cost of hiring a boat is a linear function of the number of hours. Hiring the boat for 2 hours costs $45, and hiring it for 5 hours costs $90. What is the cost, in dollars, of hiring it for 8 hours?
Answer: 135
The rate is (90 − 45)/(5 − 2) = 15 dollars per hour, so 8 hours cost 90 + 15(3) = 135.
Common wrong answers
- If you answered 120
- 120 is 15 × 8, forgetting the $15 fixed charge.
- If you answered 144
- 144 scales 45 by 8/2.5, a misreading.
- If you answered 180
- 180 doubles the 5-hour price, treating the cost as proportional.
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