The hours it takes Kristen to travel the same distance Marian travelled is 19.5 hours.
The average speed of Marian is 65 miles per hour for 15 hours. Therefore, her distance travelled can be calculated as follows:
speed = distance / time
Therefore,
distance = time × speed
distance = 15 × 65
distance = 975 miles
Kristen travelled at an average speed of 50 miles per hour. Kristen covers the same distance with Marian. Therefore, the hours it takes Kristen to travel the same distance Marian travelled can be calculated as follows: