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Alex and Brenda both stand at point X. Alex begins to walk a

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Joined: 27 Jan 2016
Posts: 150

Kudos [?]: 79 [0], given: 124

Schools: ISB '18
GMAT 1: 700 Q50 V34
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Re: Alex and Brenda both stand at point X. Alex begins to walk a [#permalink]

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New post 18 Jul 2017, 03:44
Marcab wrote:
Can you please let me know where am I committing mistake?
Alex already covered 4 miles. In the next t hours the total distance covered by Alex will be 4+4t.
Similarly Brenda covers Rt miles in the next t hours.
Therefore, Rt=2(4+4t)t
t=8/(R-8)


Even i committed the same mistake, you have considered the time, which Brenda has spent commuting, but the question asks the amount of time,Alex has spent walking, which is 1 hr more than what brenda has spent

so 8/r-8 +1 = r/r-8

Kudos [?]: 79 [0], given: 124

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Kudos [?]: 1050 [0], given: 5

Re: Alex and Brenda both stand at point X. Alex begins to walk a [#permalink]

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New post 11 Dec 2017, 09:54
enigma123 wrote:
Alex and Brenda both stand at point X. Alex begins to walk away from Brenda in a straight line at a rate of 4 miles per hour. One hour later, Brenda begins to ride a bicycle in a straight line in the opposite direction at a rate of R miles per hour. If R > 8, which of the following represents the amount of time, in terms of R, that Alex will have been walking when Brenda has covered twice as much distance as Alex?

A. R-4
B. R/(R+4)
C. R/(R-8)
D. 8/(R-8)
E. 2R - 4


We are given that Alex has a rate of 4 mph and Brenda has a rate of R mph. We are also given that Alex begins to walk away from Brenda in a straight line at a rate of 4 mph. One hour later, Brenda begins to ride a bicycle in a straight line in the opposite direction. Thus, we can let Alex’s time = T + 1 and Brenda’s time = T.

Finally, since distance = rate x time, Alex’s distance = 4(T + 1) = 4T + 4 and Brenda’s distance = RT. We need to determine the amount of time it takes Brenda to cover twice the distance Alex has gone. So, we can create the following equation and determine T:

2(4T + 4) = RT

8T + 8 = RT

8 = RT - 8T

8 = T(R - 8)

8/(R - 8) = T

Since we are asked for Alex’s time, T + 1 = 8/(R - 8) + (R - 8)/(R - 8) = R/(R - 8).

Answer: C
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Kudos [?]: 1050 [0], given: 5

Re: Alex and Brenda both stand at point X. Alex begins to walk a   [#permalink] 11 Dec 2017, 09:54

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Alex and Brenda both stand at point X. Alex begins to walk a

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