Final answer:
To calculate Patrick's average rate of speed for his return trip, divide the distance of the trip by the time it took for him to drive it. The average speed is equal to distance divided by time.
Step-by-step explanation:
To find Patrick's average rate of speed for his return trip, we need to calculate his speed. The formula for speed is distance divided by time. In this case, the distance is the same as the distance from his grandmother's house to his home, and the time is the time it took for his return trip.
Given that Patrick took 4 hours and 15 minutes for his return trip, we need to convert this time to hours. There are 60 minutes in an hour, so 15 minutes is equivalent to 15/60 = 0.25 hours. Therefore, the total time in hours is 4 + 0.25 = 4.25 hours.
Now, we know that the distance for the return trip is the same as the distance from Patrick's grandmother's house to his home. Since the distance for the initial trip was not provided, we can assume it is the same as the return trip. Therefore, we can use the distance and time for the return trip to calculate the average rate of speed:
Average speed = Distance / Time
Since the distance is the same and we have both distances and times in hours, the average speed for Patrick's return trip is:
Average speed = Distance / Time = Distance / 4.25 = Distance / 4.25