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Updated on: 21 Aug 2013, 02:51
Originally posted by AMITAGARWAL2 on 20 Aug 2013, 18:22.
Last edited by Bunuel on 21 Aug 2013, 02:51, edited 1 time in total.
Last edited by Bunuel on 21 Aug 2013, 02:51, edited 1 time in total.
Edited the question.
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
64% (03:04) correct
36%
(03:20)
wrong
based on 290
sessions
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Not Attempted Yet
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 30 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?
A. 36
B. 72
C. 132
D. 144
E. 180
A. 36
B. 72
C. 132
D. 144
E. 180
21 Aug 2013, 03:03
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AMITAGARWAL2
The amount of time it takes bus B to cover the exact distance that bus A has covered:
The distance covered by bus B = 80t = the distance covered by bus A = 30(t+1) = --> 80t = 30(t+1) --> t=3/5 hours.
The amount of time it takes bus B to cover twice the distance that bus A has covered:
The distance covered by bus B = 80T = twice the distance covered by bus A = 2*30(T+1) --> 80T = 2*30(T+1) --> T=3 hours.
T - t = 3 - 3/5 = 12/5 hours = 144 minutes.
Answer: D.
Similar question to practice: alex-and-brenda-both-stand-at-point-x-alex-begins-to-walk-a-128752.html (good one)
Hope it helps.
General Discussion
20 Aug 2013, 19:14
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AMITAGARWAL2
1st part: - In 1hr, Bus A covers 30 miles.
Relative speed of bus A & Bus B is (80-30) = 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 = 144min
