Question 131·Medium·Linear Inequalities in One or Two Variables
A city transit system sells a monthly pass for $96. Without the pass, each bus ride costs $2.75.
Which inequality can be solved to find , the least number of bus rides in a month for which buying the monthly pass is less expensive than paying per ride?
For cost-comparison word problems, first write a clear algebraic expression for each option in terms of the variable (here, ). Then carefully translate the key comparison phrase—such as "less than," "more than," or "no more than"—into an inequality by putting the correct expression on each side of the symbol. Finally, check that the inequality matches the real-world situation (fixed fee vs. per-use fee) and that you did not reverse the inequality sign or misuse multiplication/addition with the variable.
Hints
Identify the two ways to pay
Think about the total cost with the pass and the total cost without the pass (paying per ride). How can you write each cost using ?
Use per-ride cost correctly
Each ride costs dollars. For rides, should you add once, or multiply by ?
Translate the words into symbols
The problem asks for when the monthly pass is less expensive than paying per ride. Which side of the inequality should represent the pass cost, and which side should represent the pay-per-ride cost?
Desmos Guide
Enter the cost of the monthly pass
In Desmos, type y1 = 96. This horizontal line represents the constant cost of using the monthly pass, no matter how many rides you take.
Enter the cost of paying per ride
Type y2 = 2.75x. This line represents the total cost of paying per ride, where is the number of rides and the cost increases as increases.
Compare the two graphs
Look for the -values where the graph (paying per ride) is above the graph (monthly pass). Those -values show when paying per ride costs more than the pass, which corresponds to the inequality where the fixed pass cost is less than the per-ride cost expression.
Step-by-step Explanation
Write expressions for each cost
For bus rides:
- Cost with the monthly pass is always dollars (it does not depend on ).
- Cost without the pass is dollars per ride, so the total is dollars.
Translate the phrase into an inequality
We want the number of rides for which buying the monthly pass is less expensive than paying per ride.
- Let "cost with pass" be on the left.
- Let "cost without pass" be on the right.
- "Pass is less expensive than paying per ride" becomes:
So in symbols we have: .
Substitute the actual expressions
Now replace each phrase with the expression you found:
- Pass cost is .
- Per-ride cost is .
So the inequality becomes
This matches answer choice A) .