Final answer:
The average speed of the entire trip, excluding the 30-minute stop, is calculated by dividing the total distance travelled (250 miles) by the total time spent driving (4.5 hours), resulting in approximately 55.6 miles per hour.
Step-by-step explanation:
To calculate the average speed of the entire trip, we need to find the total distance travelled and divide it by the total time taken, excluding any stops as they do not contribute to the movement. The total distance travelled is the sum of the two segments: 150 miles + 100 miles, which equals 250 miles. The total time spent driving is the sum of the two segments as well: 3 hours + 1.5 hours, which equals 4.5 hours. Since time is typically counted in hours when calculating speed, the 30-minute stop is irrelevant to the average speed calculation.
Average speed is thus calculated as Total distance divided by Total time, which in this case is 250 miles ÷ 4.5 hours.
Now, let's do the calculation: 250 miles ÷ 4.5 hours = 55.55 miles per hour (mph), which we can round to 55.6 mph. Therefore, the average speed over the entire trip was approximately 55.6 mph.