Final answer:
The Zimmerman's will take approximately 13 hours to travel 715 miles at 55 miles per hour. They depart at 6:00 am, so they are expected to arrive at their grandparents' house around 7:00 pm.
Step-by-step explanation:
To calculate the time the Zimmerman's will arrive at their grandparents' house, we need to determine how long it will take them to drive 715 miles at an average speed of 55 miles per hour.
The formula for travel time is:
Time = Distance ÷ Speed
The Zimmerman's are travelling a distance of 715 miles at an average speed of 55 miles per hour. Thus, the travel time can be calculated as follows:
Time = 715 mi ÷ 55 mi/hr
Time = 13 hours
If they leave at 6:00 am, adding 13 hours to this start time brings us to 7:00 pm. Therefore, the Zimmerman's should tell their grandparents to expect them at around 7:00 pm.