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# Switches

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Senior Manager
Joined: 16 Apr 2009
Posts: 251
Schools: Ross
Followers: 1

Kudos [?]: 21 [0], given: 10

Switches [#permalink]  14 Aug 2009, 06:52
00:00

Difficulty:

(N/A)

Question Stats:

33% (04:25) correct 67% (01:38) wrong based on 12 sessions
One-fifth of the light switches produced by a cer¬tain factory are defective. Four-fifths of the defective switches are rejected and 1/20 th of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

_________________

Keep trying no matter how hard it seems, it will get easier.

Last edited by vannu on 14 Aug 2009, 08:46, edited 1 time in total.
Current Student
Joined: 18 Jun 2009
Posts: 361
Location: San Francisco
Followers: 8

Kudos [?]: 62 [0], given: 15

Re: Switches [#permalink]  14 Aug 2009, 07:55
vannu wrote:
One-fifth of the light switches produced by a cer¬tain factory are defective. Four-fifths of the defective switches are rejected and of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

I guess there is somethings missing here "Four-fifths of the defective switches are rejected and of the nondefective switches are rejected by mistake"
Manager
Joined: 25 Jul 2009
Posts: 117
Schools: NYU, NUS, ISB, DUKE, ROSS, DARDEN
Followers: 4

Kudos [?]: 143 [0], given: 17

Re: Switches [#permalink]  14 Aug 2009, 07:59
vannu wrote:
One-fifth of the light switches produced by a cer¬tain factory are defective. Four-fifths of the defective switches are rejected and of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

There seems to be some missing data in the highlighted part.
_________________

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My GMAT Debrief - 740 (Q50, V39) | My Test-Taking Strategies for GMAT | Sameer's SC Notes

Intern
Joined: 14 Aug 2009
Posts: 1
Followers: 0

Kudos [?]: 1 [0], given: 4

Re: Switches [#permalink]  14 Aug 2009, 08:46
i too got confused by the highlighted sentence.. is the prblm statemnt clear..
Senior Manager
Joined: 16 Apr 2009
Posts: 251
Schools: Ross
Followers: 1

Kudos [?]: 21 [0], given: 10

Re: Switches [#permalink]  14 Aug 2009, 08:47
I edited the question. Sorry for the inconvenience.
_________________

Keep trying no matter how hard it seems, it will get easier.

SVP
Joined: 05 Jul 2006
Posts: 1542
Followers: 5

Kudos [?]: 70 [1] , given: 39

Re: Switches [#permalink]  14 Aug 2009, 08:58
1
KUDOS
vannu wrote:
One-fifth of the light switches produced by a cer¬tain factory are defective. Four-fifths of the defective switches are rejected and 1/20 th of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

assume 1000 produced

200 defective , 160 defective and rejected, 40 nondefective rejected by mistake

40 defective and not rejected , 760 non defective and not rejected, total non rejected and sold = 800

percent of the switches sold by the factory are defective = 40/800*100 = 5%
Manager
Joined: 25 Jul 2009
Posts: 117
Schools: NYU, NUS, ISB, DUKE, ROSS, DARDEN
Followers: 4

Kudos [?]: 143 [0], given: 17

Re: Switches [#permalink]  14 Aug 2009, 09:03
vannu wrote:
One-fifth of the light switches produced by a cer¬tain factory are defective. Four-fifths of the defective switches are rejected and 1/20 th of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

Assume x as the number of switches and that x =100
Defective Switches = 1/5 * 100 = 20
Defective Switches that are rejected = 4/5 * 20 = 16
Defective Switches that are sold = 20 - 16 = 4

Non-defective Switches = 100 - 20 = 80
Non-defective Switches mistakenly rejected = 80*1/20 = 4
Non-defective Switches that are sold = 80 - 4 = 76

Total sold in the market = 76 + 4 = 80
% of defective = (4/80)*100 = 5%

ANS: B
_________________

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My GMAT Debrief - 740 (Q50, V39) | My Test-Taking Strategies for GMAT | Sameer's SC Notes

Senior Manager
Joined: 15 Feb 2011
Posts: 263
Followers: 4

Kudos [?]: 20 [0], given: 9

Re: Switches [#permalink]  10 Jul 2011, 10:40
This may be a very stupid question but please help me understand how did we derive at(4/80)*100 ??

Is there a formula for this??
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2047
Followers: 128

Kudos [?]: 903 [0], given: 376

Re: Switches [#permalink]  10 Jul 2011, 11:04
vannu wrote:
One-fifth of the light switches produced by a certain factory are defective. Four-fifths of the defective switches are rejected and 1/20 th of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?
(A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
[Reveal] Spoiler:
B

 Rejected Not Rejected Defective a b c Not Defective d e f g h i

Fill in this order:
i=100
1/5 of total= Defective i.e. 1/5*100=20 Defective. c=20
Not Defective=100-20=80, f=80

4/5 of Defective=Rejected= 4/5*20=16. a=16
b=c-a i.e. b=20-16=4

1/20 th of the nondefective switches are rejected
1/20*80=4. d=4
g=a+d=16+4=20

h=i-g=100-20=80

Defective+Not Rejected=b=4
Total Not Rejected=h=80

%=4/80*100=5

 Rejected Not Rejected Defective 16 4 20 Not Defective 4 e 80 20 80 100

Ans: "B"
_________________
Senior Manager
Joined: 15 Feb 2011
Posts: 263
Followers: 4

Kudos [?]: 20 [0], given: 9

Re: Switches [#permalink]  10 Jul 2011, 11:15
thanks fluke, dis approach did help me understand the question better...

this was my first post..i have couple of more questions wherein i need your advice..pls suggest if i need to open up a new topic for every question or can i post my queries alongside the existing post..like what i did in this one..

thanks again!!
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2047
Followers: 128

Kudos [?]: 903 [0], given: 376

Re: Switches [#permalink]  10 Jul 2011, 11:51
DeeptiM wrote:
thanks fluke, dis approach did help me understand the question better...

this was my first post..i have couple of more questions wherein i need your advice..pls suggest if i need to open up a new topic for every question or can i post my queries alongside the existing post..like what i did in this one..

thanks again!!

Please reply to the existing post. If the question is not discussed before, create a new thread.
_________________
Re: Switches   [#permalink] 10 Jul 2011, 11:51
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# Switches

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