Position of the car at t1=5 sec is x1=0.8 km (from graph).
Position of the car at t2=10 sec is x2=1 km (from graph).
The distance travel by the car between time interval 5 sec to 10 is given as,
The average speed of the car between the time interval 5 sec to 10 sec is given as,
Therefore, the average speed of the car between the time interval 5 and 10 sec is 0.04 km/s.