Final answer:
The speed of an airplane that travels 400 miles in 8 hours is determined by dividing the distance by time. The calculation yields a speed of 50 mph, which is option (a) as the correct answer.
Step-by-step explanation:
The question is asking to determine the rate that best represents the relationship between the distance an airplane has traveled and the time taken. To calculate this rate, which is also known as the speed, we would divide the total distance traveled by the time taken to cover that distance.
For an airplane that travels 400 miles in 8 hours, the calculation to find the speed is as follows:
Speed = Distance / Time
Speed = 400 miles / 8 hours = 50 mph
Therefore, the rate that best represents the relationship between the distance traveled by the airplane and the time is option (a) 50 mph.