Solve the problem.
-On a recent trip, Sarah's car traveled 20 mph faster on the first 120 miles than it did on the remaining 80 miles. The total time for the trip was 4 hr. Find the speed of Sarah's car on the first part of the trip.
A)10 mph
B)60 mph
C)35 mph
D)40 mph

Question

Quizplus · Accepted Answer

Let the speed of the car on the remaining 80 miles be x mph. Then, the speed on the first 120 miles is x + 20 mph. The time to travel the first 120 miles is 120 / (x + 20), and the time to travel the remaining 80 miles is 80 / x. The total time is 4 hours, so we have the equation: 120 / (x + 20) + 80 / x = 4. Solving this equation for x gives us the speed on the slower part of the trip, and adding 20 to that gives us the speed on the first part of the trip, which is 60 mph.

Solve the Problem. -On a Recent Trip, Sarah's Car Traveled 20 Mph Faster