Sara's mom takes the parkway to work. It takes her 30 minutes to travel from mile marker 88 where she enters to her exit at mile marker 121. What is her average speed?

4.0 mph

16.5 mph

33 mph

66 mph

To figure speed you must find the distance and the time

To find the distance in this instance you must subtract mile marker 88 from 121

121 - 88 = 33

And the time is 30 minutes, but since your looking for miles per _hour_. You must convert it

30 minutes = 0.5 hours

Lastly, you divide distance over the time

33/0.5 = 66 mph