Final answer:
To determine the car's average rate during the second part of the trip, we subtract the distance covered in the first part from the total distance and divide the remaining distance by the time left. The calculation shows an average rate of 60 mph for the second part.
Step-by-step explanation:
To solve this problem, we first need to calculate the distance covered during the first part of the trip. Since the car travels at an average rate of 55 miles per hour for 4 hours, we can find this distance by multiplying the speed by the time.
Distance = Speed × Time = 55 mph × 4 h = 220 miles.
Since the total distance of the trip is 700 miles, the remaining distance of the second part of the trip is 700 miles - 220 miles = 480 miles. The total time for the trip is 12 hours, and the car has already spent 4 hours on the first part, so the time taken to travel the remaining distance is 12 h - 4 h = 8 hours.
To find the average rate during the second part, we divide the remaining distance by the time it takes:
Average rate = Distance / Time = 480 miles / 8 h = 60 mph.
Therefore, the car's average rate during the second part of the trip is 60 mph, which corresponds to option C).