Sarah is driving to the airport. After driving at 20 miles per hour for one hour, she realizes that if she continues at that same average rate she will be an hour late for her flight. She then travels 50 miles per hour for the rest of the trip, and arrives 30 minutes before her flight departs. How many miles did she drive in all? Choose the most appropriate option.
A) 140
B) 175
C) 210
D) 70
E) 280
After driving at 20 miles per hourfor one hour, this distance left to cover is d-20. Say this distance is x miles.   Now, we know that the difference in time between covering this distance at 20 miles per hour and 50 miles per hour is 1+ 1/2 = 3/2 hours.   So, we have that x/20 - x/50 = 3/2 --&gt; 5x/100 - 2x/100 = 3/2 --&gt; 3x/100 = 3/2 --&gt; x = 50.   Total distance = x + 20 = 70 miles.   Answer: 70
<result>D</result>
Sarah is driving to the airport. After driving at 20 miles per hour for one hour, she realizes that if she continues at that same average rate she will be an hour late for her flight. She then travels 50 miles per hour for the rest of the trip, and arrives 30 minutes before her flight departs. How many miles did she drive in all?