The average speed of an object is obtained by dividing the total distance travelled by the total time taken.
That is, average speed = Total distance travelled / Total time taken
If an object travels a distance s in time t then
its speed v is,
v = s/t
Let us understand this by an example. A car travels a distance of 100 km in 2 h. Its average speed is 50 km h–1. The car might not have travelled at 50 km h–1 all the time. Sometimes it might have travelled faster and sometimes slower than this.