<span>Boiling water.The heat passes from the burner into the pot, heating the water at the bottom. Then, this hot water rises and cooler water moves down to replace it, causing a circular motion.</span>
Deleted this answer, sorry for any inconveniences that it may have caused.
Speed (velocity)=distance/time
V1=98km/4hr=24.5km/hr
V2=61km/3hr=20.3km/hr
Average speed (velocity)=total velocity/ number
Average speed (velocity)=44.8km/hr/2=22.4
So the average speed is 22.4km/hr