Given that the distance is d = 72 km and the time is t = 1 hour.
We have to find the speed in m/s.
First, we have to convert the unit of distance in m and the unit of time in seconds.
The distance will be

The time will be

The speed can be calculated by the formula

Substituting the values, the speed will be

Thus, the speed of the car is 20 m/s