Two cars started from the same point, at 5 am, traveling in opposite directions at 40 and 50 mph respectively. At what time will they be 450 miles apart?  Pick one:
A) 8 am
B) 10 am
C) 11 am
D) 12 am
E) 14 am

Rationale: after t hours the distances d 1 and d 2 , in miles per hour , traveled by the two cars are given by d 1 = 40 t and d 2 = 50 t after t hours the distance d separating the two cars is given by d = d 1 + d 2 = 40 t + 50 t = 90 t distance d will be equal to 450 miles when d = 90 t = 450 miles t = 5 hours . 5 am + 5 hours = 10 am answer : b
Answer: B