The distance from City A to City B is 60 miles. While driving from City A to City B, Bob drives at a constant speed of 40 miles per hour. Alice leaves City A 30 minutes after Bob. What is the minimum constant speed in miles per hour that Alice must exceed in order to arrive in City B before Bob?
Choose the correct choice from the following choices.
A) 45 B) 48 C) 50 D) 52 E) 60
The time it takes Bob to drive to City B is 60 / 40= 
<gadget id="calculator">60 / 40</gadget>
<output>3/2 = around 1.5</output>
1.5 hours.   Alice needs to take less than 1 hour for the trip.   Alice needs to exceed a constant speed of 60 / 1= 
<gadget id="calculator">60 / 1</gadget>
<output>60</output>
60 miles per hour.   The answer is 60.
<result>E</result>
The distance from City A to City B is 60 miles. While driving from City A to City B, Bob drives at a constant speed of 40 miles per hour. Alice leaves City A 30 minutes after Bob. What is the minimum constant speed in miles per hour that Alice must exceed in order to arrive in City B before Bob?