A car drives 60 miles on local roads at 20 mph, and 120 miles on the highway at 60 mph, what is the average speed of the entire trip?
Select the correct option.
A) 36 mph
B) 40 mph
C) 44 mph
D) 52 mph
E) 58 mph

Rationale: "so the answer is plainly a . . . . we have a general relation for speed , time and distance : v ( velocity ) * t ( time ) = d ( distance ) for first part we have d = 60 miles , and v = 20 mph so we can obtain time : 20 * t = 60 or t = 60 / 20 = 3 hours the needed time to cover 60 miles in the same way we should divide 120 to 60 to find the needed time to cover 120 miles , so t = 2 hours so the total time for covering total distance would be 3 + 2 = 5 hours and total distance is 60 + 120 = 180 miles final stage : average speed is total distance divide to total time : 180 / 5 = 36 miles per hour . . . ."
Answer: A