Julie recently drove to visit her parents who live 120 miles away. On her way there her average speed was 20 miles per hours then on her way home she ran into some bad weather. If Julie spent a total of 5 hours driving, find two rates?

1 Answer
Oct 29, 2016

Based on an assumption that the outward speed was #60mph#, The speed for the return journey was #40 mph#


There is a problem with the information. That speed on the outward joureny gives a time for 6 hours just for the first part.

Let's assume that The outward speed was #60mph#......

For the entire journey there and back we know the total distance (120 miles) and the total time (5 hours), so we can calculate the average speed.

#"Ave Speed" = "Total Distance"/"Total time" = 240/5 = 48 mph#

However, we need to work with the two parts separately.

#S = D/T " " T= D/S " " D = S xx T#

Outward Journey: # T = 120 /60 = 2" "# hours

This means that for the return journey the time was #3# hours.

Her speed was lower, because the drive took longer.

#S = D/T = 120/3 = 40mph#

NOte: This is based on the an assumption of the outward speed.

If it was different, the calculations remain the same, just with new values.