two trucks leave a warehouse at the same time.

Question

Two trucks leave a warehouse at the same time. One travels due north at an average speed of 58 miles per hour, and the other travels due south at an average speed of 48 miles per hour. After how many hours will the two trucks be 424 miles apart. 

Answer 1

Distance = Rate x Time

 

in this case, D = 424 miles

 

because each driver will drive for the same length of time, we can use their average rate

 

so, D = average rate x Time

 

424 miles = (58mph + 48mph)/2 x Time

 

424 miles / 53mph = 8 hours

 

Since the total time is 8 hours, each driver will drive for 4 hours.

 

Proof: 58mph x 4h + 48mph x 4h = 232m + 192m = 424 miles