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# Help: Flashcard GMAT problem

Author Message
Intern
Status: "
Joined: 22 Jan 2011
Posts: 42

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Schools: IE- ESCP - Warwick

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18 Apr 2011, 22:25
00:00

Difficulty:

45% (medium)

Question Stats:

9% (00:06) correct 91% (00:45) wrong based on 11 sessions

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A swimmer makes a round trip up and down the
river which takes her X hours. If the next day she
swims the same distance with the same speed in
still water, which takes her Y hours, which of the
following statements is true?
 X>Y
 X<Y
 X=Y
 X= 1.5 Y

I really need help for that one, as for me no assumptions can be made. How do we know that in the first situation the swimmer is faster?

[Reveal] Spoiler: OA

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Manager
Joined: 18 Jan 2011
Posts: 228

Kudos [?]: 37 [0], given: 4

Re: Help: Flashcard GMAT problem [#permalink]

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18 Apr 2011, 22:40
Discussed here. OA here seems to be incorrect.

m03-q-71568.html
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Kudos [?]: 37 [0], given: 4

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 1964

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Re: Help: Flashcard GMAT problem [#permalink]

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18 Apr 2011, 22:56
ravsg wrote:
Discussed here. OA here seems to be incorrect.

m03-q-71568.html

Thanks ravsg for pointing to the right thread. Really appreciated.

Also discussed here:
m03-111523.html
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Joined: 16 Nov 2010
Posts: 1594

Kudos [?]: 592 [0], given: 36

Location: United States (IN)
Concentration: Strategy, Technology
Re: Help: Flashcard GMAT problem [#permalink]

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18 Apr 2011, 23:34

Y = 2D/V

X = D/(V-p) + D/(V+p)

p -> Speed of river

D(V+p + V -p)
-------------
V^2 - p^2

= 2DV/(V^2 - p^2)

Y - X = 2D/V - 2DV/(V^2 - p^2)

=2D( V^2 - p^2 - V^2)/(V^2 - p^2)

= -p^2D/(V^2 - p^2) which is negative

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Re: Help: Flashcard GMAT problem [#permalink]

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30 Apr 2011, 20:44
D= 10, Swimmer speed = a = 2 and still water speed = 1
x = 10/(2-1) + 10/(2+1)
= 13.33
y = 10/2 + 10/2
= 10

x>y.
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Re: Help: Flashcard GMAT problem   [#permalink] 30 Apr 2011, 20:44
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