Tom leaves the outskirts of City A at 8 am and travels north to City B at a constant speed of 80 km/h. Cindy leaves from the same place at 8:30 am and takes the same route traveling at a constant speed of 100 km/h. At what time will Cindy overtake Tom along the road to Sydney?
Tom has a 40 km head start
... 80 km/h * .5 h
Cindy is catching up at 20 km/h
... 100 km/h - 80 km/h