Car A leaves the airport at 8:00 am and travels at a constant rate of 40 km per hour. Car B leaves the airport at 8:45 am and travels in the same direction along the same highway at a constant rate of 52 km per hour. At what time will Car B be 9 km ahead of Car A?  Choose the correct choice from the following.
A) 11:00 am  B) 11:15 am  C) 11:30 am  D) 11:45am  E) 12:00 noon
At 8:45 am, Car A will be 30 km ahead of Car B.   Car B travels at a rate 12 km per hour faster than Car A.   Car B needs to travel 39 km more than Car A in order to be 9 km ahead.   This will take 39 km/12 km per hour=3.25 hours.   Car B will be 9 km ahead at 12:00 noon.   The answer is 12:00 noon.
<result>E</result>
Car A leaves the airport at 8:00 am and travels at a constant rate of 40 km per hour. Car B leaves the airport at 8:45 am and travels in the same direction along the same highway at a constant rate of 52 km per hour. At what time will Car B be 9 km ahead of Car A?