To find the average speed of the girl for the entire trip, we need to calculate the total distance covered and the total time taken.
Distance covered during running = speed x time = 5 m/s x 2 s = 10 m
Distance covered during walking = speed x time = 4 m/s x 3 s = 12 m
Distance covered during biking = speed x time = 10 m/s x 5 s = 50 m
Total distance covered = 10 m + 12 m + 50 m = 72 m
Total time taken = 2 s + 3 s + 5 s = 10 s
Average speed = Total distance covered / Total time taken
= 72 m / 10 s
= 7.2 m/s