Answer:
To find the average speed of the truck, we can divide the total distance travelled by the total time taken.
Average speed = Total distance / Total time
In this case, the truck travelled 261 miles in 4 hours.
Average speed = 261 miles / 4 hours
Average speed = 65.25 mph (rounded to two decimal places)
Therefore, the truck was averaging approximately 65 mph on this trip.
The correct option is (a) 65 mph.