Answer:approximately 58.76 kilometers per hour.
Explanation:
The driver traveled from city A to city B in 1 hour and 13 minutes, which is a total of 73 minutes. During this time, he had to stop at 5 traffic signals, with an average time of 80 seconds per signal. Therefore, the total time the driver spent waiting at traffic signals is:
5 signals x 80 seconds per signal = 400 seconds
To calculate the total time the driver spent driving, we need to subtract the time spent waiting at traffic signals from the total time of the trip:
Total driving time = Total trip time - Time spent waiting at signals
= 73 minutes x 60 seconds per minute - 400 seconds
= 4380 seconds - 400 seconds
= 3980 seconds
Now we can calculate the average driving speed:
Average speed = Distance / Time
Since the distance between the cities is 65 kilometers and the time spent driving is 3980 seconds (or 1.106 hours), we have:
Average speed = 65 km / 1.106 hours = 58.76 km/h
Therefore, the average driving speed was approximately 58.76 kilometers per hour.