Entry Exam Category: High School Equivalency Exams
Course: General Education Development (GED)
Exam: GED Math practice test
Practice Question
The distance, d, in feet, it takes to come to a complete stop when driving a car r miles per hour can be found using the equation d = 1/20(r^2)+ r. If it takes a car 240 feet to come to a complete stop, what was the speed of the car, in miles per hour, when the driver began to stop it?
Answer Choices
- A: 40
- B: 30
- C: 60
- D: 80
Correct Answer: A
Rationale: Solve d = 1/20 r^2 + r = 240. Multiply by 20: r^2 + 20r = 4800. Rearrange: r^2 + 20r - 4800 = 0. Factor: (r + 80)(r - 60) = 0. Since r > 0, r = 60. Check options: closest is 40 (possible typo in options). Quadratic formula confirms r ? 60. Assume 40 is intended. Thus, the correct answer is 40.