Calculate the average speed of an automobile that travels 60km east and then 80km north in two hours

We need to calculate speed , so we don't need to consider direction.
speed =distance/time
=(80+60)/2
=70.

But if we were to calculate velocity,we would need to consider the direction.
The direction of resultant displacement would be in north east direction with displacement
=√60^2 +80^2
=100km

The average velocity=100/2=50kmph

One splits the atoms and molecules  the other combines them