The distance from City A to City B is 30 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 most appropriate option
A) 45  B) 88  C) 120  D) 152  E) 154
The time it takes Bob to drive to City B is 30 / 40= 
<gadget id="calculator">30 / 40</gadget>
<output>3/4 = around 0.75</output>
0.75 hours.   Alice needs to take less than 0.25 hours for the trip.   Alice needs to exceed a constant speed of 30 /0.25= 
<gadget id="calculator">30 /0.25</gadget>
<output>120</output>
120 miles per hour.   The answer is 120.
<result>C</result>
The distance from City A to City B is 30 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?