Divide the distance by the miles per hour:
Kim: 240 miles / 60 miles per hour = 4 hours
Robert: 240 miles / 50 miles per hour = 4.8 hours = 4 hours 48 minutes
Barb: 240 miles / 80 miles per hour = 3 hours.
Now find the time they need to leave by subtracting the travel time from the arrival time:
Kim needs to leave at 9:30 am
Robert needs to leave at 8: 42 am
Barb needs to leave at 10: 30 am
