Buses A and B start from a common bus stop X. Bus A begins to travel in a straight line away from bus B at a constant rate of 20 miles per hour. One hour later, bus B begins to travel in a straight line in the exact opposite direction at a constant rate of 80 miles per hour. If both buses travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes bus B to cover the exact distance that bus A has covered and the amount of time it takes bus B to cover twice the distance that bus A has covered?
Choose the correct choice from the following answers:
A) 36
B) 72
C) 132
D) 144
E) 180
1st part: - In 1hr, Bus A covers 30 miles.   Relative speed of bus ABus B is   (80-30)= 
<gadget id="calculator">  (80-30)</gadget>
<output>50</output>
50mph.   So time required for Bus B to cover the exact distance as A is   50*t= 30   t=3/5 = 36min   2nd part   80*t=2d - B has to cover twice the distance   30*(t+1) = d - A traveled 1hr more and has to travel only only d   so   d/30 - 2d/80 = 1   D=120   T= 3hrs = 180 min   Question asks for +ve difference between part 1 and part 2 in minutes   = 180-36 = 132min   132
<result>C</result>
Buses A and B start from a common bus stop X. Bus A begins to travel in a straight line away from bus B at a constant rate of 20 miles per hour. One hour later, bus B begins to travel in a straight line in the exact opposite direction at a constant rate of 80 miles per hour. If both buses travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes bus B to cover the exact distance that bus A has covered and the amount of time it takes bus B to cover twice the distance that bus A has covered?