Answer:
65 mph
Explanation:
To calculate the average speed of Niamh's car, we need to use the formula:
Average speed = Total distance ÷ Total time
First, we need to calculate the total time elapsed from 17:30 to 19:42:
Total time = 19:42 - 17:30 = 2 hours and 12 minutes
To convert the minutes to decimal form, we divide by 60:
2 hours and 12 minutes = 2 + (12 ÷ 60) = 2.2 hours
Now we can calculate the average speed:
Average speed = Total distance ÷ Total time
Average speed = 143 miles ÷ 2.2 hours
Average speed = 65 mph
Therefore, the average speed of Niamh's car from 17:30 to 19:42 was 65 mph.