Janet took 3h to drive from Town A to Town B at an average speed of 100km/h. She rested for 30 minutes and traveled to Town C at an average speed of 70km/h for the remaining 2h. Find Janet's average speed for the whole journey.
Total distance=3100+270=440km
Total time taken=3+0.5+2=5.5hr
Average speed=440/5.5=80km/hr