A linear function describes a total with a starting cost and a constant cost for each minute. Multiply the per-minute charge by the number of minutes, then add the one-time fee. Don't swap their jobs: the fee is paid once, while the rate repeats for every minute.
Hints
- Hint 1
A linear cost function has a constant term that stays the same and a term that changes with the number of minutes. Which terms in the proposed rules are multiplied by ?
- Hint 2
A unit rate is the change in cost for one more minute. In , the coefficient gives that change. Compare the coefficients in the proposed rules with the charge for one minute.
Step-by-step
Add the fixed fee to the minute charge
Step 1Find the starting cost
No Desmos needed. The words give the fee and the per-minute rate directly. The flat fee is charged once, even if the ride lasts minutes, so . Don't multiply that fee by .
- Step 2
Find the charge for minutes
The unit rate, or cost for one minute, is $0.50. Multiply it by minutes to get the changing part of the cost: .
- Step 3
Write the total-cost function
Add the minute charge to the flat fee to get the total cost: . The rate multiplies minutes; the fee is added once. This function gives the ride's total cost in dollars. Choice D.