a)
The average speed is equal to the ratio between the total distance ( and the total time taken (
):
the distance travelled by the trucker in the first 3 hour can be written as the time multiplied by the velocity:
So the total distance is
The total time is equal to the first 3 hours + the time taken to cover the following 20 miles in the city:
So, the equation can be rewritten as:
b) 0.50 h (half a hour)
Since we know the value of the average speed, , we can substitute it into the previous equation to find the value of
, the time the trucker drove in the city: