Explanation:
The cart with Low fan speed :
Elapsed time to finish line, t = 7.4 s
Total distance, d = 500 cm
Average speed,
v = 67.56 cm/s
or
v = 67.6 cm/s
The cart with Medium fan speed :
Elapsed time to finish line, t = 6.4 s
Total distance, d = 500 cm
Average speed,
v = 78.12 cm/s
v = 78.1 cm/s
The cart with High fan speed :
Elapsed time to finish line, t = 5.5 s
Total distance, d = 500 cm
Average speed,
v = 90.90 cm/s
or
v = 90.9 cm/s
Hence, this is the required solution.