21) on the first day of his cross-country trip, mike drove 100 miles in 2 hours before stopping for lunch. After lunch, he drove 420 miles in 6 hours. What was average speed in miles per hour for his 8 hours of driving?

Average speed = 65 miles per hour

Step-by-step explanation:

Mike drove 100 miles in 2hrs

He stopped to take lunch then;

drove 420 miles in 6hrs

Total distance covered = 100 + 420 miles = 520 miles

Total time taken = 2 + 6 hrs = 8hrs

Average speed = Total distance : total time = 520/8 = 65 miles per hour