Final answer:
To find the average speed for the entire trip, divide the total distance by the total time. In this case, the average speed is 30 mph.
Step-by-step explanation:
To find the average speed for the entire trip, we need to consider the total distance covered and the total time taken.
Let's assume the distance to point A is 'd' miles.
At a speed of 30 mph, the time taken to reach point A is d/30 hours.
For the entire trip (to point A and back), the total distance covered is 2d miles.
To find the average speed, we divide the total distance by the total time:
Average speed = 2d / (d/30 + d/30) = 2d / (2d/30) = 2d * 30 / 2d = 30 mph
Therefore, the answer is D) 30 mph.