Final answer:
The average speed for the 8 km trip is 37.556 km/h.
Step-by-step explanation:
To find the average speed for the 8 km trip, we need to calculate the total time taken and the total distance traveled. The first 4 km is traveled at a speed of 30 km/h, which takes 4/30 = 0.1333 hours. The second 4 km is traveled at a speed of 50 km/h, which takes 4/50 = 0.08 hours. The total time taken is 0.1333 + 0.08 = 0.2133 hours.
The total distance traveled is 4 km + 4 km = 8 km. Therefore, the average speed is calculated by dividing the total distance by the total time: 8 km / 0.2133 hours = 37.556 km/h.
So, the average speed for the 8 km trip is 37.556 km/h.