Answer:
The average speed is 22.5 km/hr and displacement is zero.
Step-by-step explanation:
Given that,
Distance of one side = 45 km
Time = 4 hrs
We need to calculate the average speed
Using formula of average speed

Where, D = total distance
T = total time
Put the value into the formula


Displacement will be zero because the journey ends where the journey stated.
Hence, The average speed is 22.5 km/hr and displacement is zero