A taxi company charges a flat fee of $3 plus $2 per mile driven.
What is the total cost, in dollars, of a 12-mile trip with this company?
For “flat fee plus per-unit rate” problems, quickly write a linear expression of the form (flat fee) (rate)(quantity), then substitute the given quantity and simplify using correct order of operations (multiply before adding). On the SAT, avoid doing steps in your head if you’re unsure—write the short expression, compute carefully, and then match your result to the answer choices.
Hints
Identify the two parts of the cost
The total cost comes from two pieces: the flat fee and the amount that depends on how many miles you travel. How is each part described?
Write a math expression
For a 12-mile trip, try to write a single expression using the flat fee $3 and the per-mile cost $2 multiplied by the 12 miles.
Use order of operations
In your expression, make sure to multiply the per-mile cost by 12 before adding the flat fee. What value do you get?
Desmos Guide
Evaluate the cost expression
In Desmos, type the expression 3 + 2*12 and press Enter. The single numeric result that appears is the total cost of the 12-mile trip in dollars.
Step-by-step Explanation
Translate the wording into an expression
The company charges a flat fee of $3 plus $2 per mile. For miles, the total cost can be written as
Here, is the number of miles driven.
Substitute the given distance
The trip is 12 miles, so substitute into the expression:
Evaluate the expression to find the total cost
First multiply the per-mile rate by the miles:
Then add the flat fee:
So, the total cost of the 12-mile trip is $27, which corresponds to choice D.