Question

On Jiamin's trip to Wisconsin, her average rate of speed for the whole 5-hour trip was 62 miles per hour. For the first two hours of her trip, she kept her average speed at 50 miles per hour Then she realized she was going to be late, so she started driving faster. What was her average speed for the last three hours of her trip?

Answer 1

The total length of Jiamin's trip was 
   distance = speed × time
   distance = (52 mi/h) × (5 h) = 260 mi

The distance Jiamin traveled in her first 2 hours was
   distance = (50 mi/h) × (2 h) = 100 mi

That means she traveled the last (260 -100) mi = 160 mi in the remaining 3 hours. Her average speed for that portion of the trip was
   speed = distance / time
   speed = (160 mi) / (3 h) = (160/3) mi/h ≈ 53 1/3 mi/h

Jiamin's average speed for the last 3 hours of her trip was 53 1/3 mi/h.