How do I find the average speed if I know the distance and the time

Question

so the problem is this: 

 

Starting at home, Jessica traveled uphill to the toy store for 12 minutes at just
10 mph. She then traveled back home along the same path downhill at a speed of 30 mph.

What is her average speed for the entire trip from home to the toy store and back?

 

 

Now I get the answer pretty much witch is:   

          4 miles

         _______

         16 minutes 

 

Now how do I get the average SPEED from this?

Answer 1

speed = miles / hour

speed = 4 miles / 16 minutes

speed = (4 miles / 16 minutes ) · (60 minutes / 1 hour)

speed = 240 miles / 16 hours

speed = 15 miles / hour

speed = 15 mph

Answer 2

Hi Dawn:

 

The definition of average speed is total distance (ground covered) divided by total time.  So, if you have the total distance and total time correctly, you just set up that ratio to get the speed, by definition.   So, good work!  (I agree with your numbers, by the way).