Lindsay & Joseph : GMAT Problem Solving (PS)
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# Lindsay & Joseph

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Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 536
Location: United Kingdom
GMAT 1: 730 Q49 V45
GPA: 2.9
WE: Information Technology (Consulting)
Followers: 74

Kudos [?]: 2983 [0], given: 217

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05 Nov 2011, 12:25
00:00

Difficulty:

25% (medium)

Question Stats:

73% (02:20) correct 27% (00:40) wrong based on 22 sessions

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Lindsay can paint 1/x of a certain room in 20 minutes. What fraction of the same room can Joseph paint in 20 minutes if the two of them can paint the room in an hour, working together at their respective rates?

A)1/3x
B) 3x/(x – 3)
C) (x – 3) / 3x
D)x / (x – 3)
E) (x – 3) / x

Correct answer is C. Any idea how to solve this guys?
[Reveal] Spoiler: OA

_________________

Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Senior Manager
Joined: 11 May 2011
Posts: 372
Location: US
Followers: 3

Kudos [?]: 95 [1] , given: 46

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05 Nov 2011, 13:00
1
KUDOS
Lindsay ->
paints 1/x of a certain room in 20 minutes or 1/3 hour,
Hence, whole room can be painted in (1/3)/(1/x) = (x/3) Hour.

Joseph ->
Lets say paints 1/y of a certain room in 20 minutes or 1/3 hour. (We have to find y in terms of x)
Hence, whole room can be painted in (1/3)/(1/y) = (y/3) Hour.

As question says, two of them can paint the room in an hour
Hence, 1/(x/3)+ 1/(y/3)= 1 hr
Simpfying for y we -> y = 3x/(x-3)

Hope it helps.
Cheers!
_________________

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Manager
Joined: 21 Aug 2010
Posts: 189
Location: United States
GMAT 1: 700 Q49 V35
Followers: 2

Kudos [?]: 98 [0], given: 141

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05 Nov 2011, 20:51
enigma123 wrote:
Lindsay can paint 1/x of a certain room in 20 minutes. What fraction of the same room can Joseph paint in 20 minutes if the two of them can paint the room in an hour, working together at their respective rates?

A)1/3x
B) 3x/(x – 3)
C) (x – 3) / 3x
D)x / (x – 3)
E) (x – 3) / x

Correct answer is C. Any idea how to solve this guys?

Lindsey and Joseph together can paint the room in 1 hour

in 20 mins they can paint 1/3 part of the room.

Lindsay alone paints 1/x part of the room in 20 mins

Take Joseph paints 1/y parts in 20 mins

1/x + 1/y = 1/3

1/y = 1/3 - 1/x = (x-3)/3x ANs C
_________________

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Re: Lindsay & Joseph   [#permalink] 05 Nov 2011, 20:51
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