Final answer:
Car B will pass Car A at 10:40 am.
Step-by-step explanation:
To find the time at which car B passes car A, we need to determine the distance car A travels before car B catches up.
Car A started at 9 am and has been traveling for one hour until car B started. So, car A has already covered a distance of 40 miles.
Now, we need to calculate the time it takes car B to cover the same distance of 40 miles. Car B is traveling at a speed of 60 mph, so using the formula: time = distance / speed, we get time = 40 miles / 60 mph = 2/3 hours.
Since car B started at 10 am, it would take 2/3 hours from 10 am to reach car A. Converting 2/3 hours to minutes, we get 40 minutes.
Therefore, car B will pass car A at 10:40 am.