A car drives 40 miles on local roads at 20 mph, and 180 miles on the highway at 60 mph, what is the average speed of the entire trip?

Question

(A) 36 mph
(B) 40 mph
(C) 44 mph
(D) 52 mph
(E) 58 mph

Answer 1

Stick to the basics!

Speed = Distance/Time

 

Solving for time:

Time taken to cover 40 miles on local roads = 40/20 = 2 hours

Time taken to cover 180 miles on the highway = 180/60 = 3 hours

Total Time = 5 hours

 

Solving for distance:

Total Distance = 40 + 180 = 220

 

Average speed = Total Distance / Total Time = 220/5 = 44 miles per hour

 

C

Answer 2

2/5(20 miles per hour) + 3/5 (60 miles per hour)= 44 miles per hour, answer C.

 

2/5 of the trip was at 20 miles per hour and 3/5 of the trip was at 60 miles per hour.  The weighted average is 44 miles per hour.  

Answer 3

40 miles at 20 miles per hour = 2 hours

 

180 miles at 60 miles per hour = 3 hours

 

220 miles taking 5 hours = 44 miles per hour

 

C