A car averages 45 mph for the first 4 hours of a trip and averages 75 mph for each additional hour. The average speed for the entire trip was 65 mph. How many hours long is the trip?
Choose the correct option:
A) 12 B) 11 C) 10 D) 9 E) 8

Rationale: "let the time for which car averages 75 mph = t 65 * ( t + 4 ) = 45 * 4 + 75 t = > 10 t = 80 = > t = 8 total duration of the trip = 8 + 4 = 12 answer a"
Answer: A