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# String of bulbs

Author Message
Director
Joined: 01 Apr 2008
Posts: 827
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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04 Jul 2009, 21:40
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Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

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A string of 10 lightbulbs is wired in such a way that if
any individual lightbulb fails, the entire string fails. If for
each individual lightbulb the probability of failing during
time period T id 0.06, what is the probability that the
string of lightbulbs will fail during time period T?
A.0.06
B.(0.06)^10
C.1-(0.06)^10
D.(0.94)^10
E.1-(0.94)^10

--== Message from GMAT Club Team ==--

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Manager
Joined: 12 Apr 2009
Posts: 198

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05 Jul 2009, 01:47
Economist wrote:
A string of 10 lightbulbs is wired in such a way that if
any individual lightbulb fails, the entire string fails. If for
each individual lightbulb the probability of failing during
time period T id 0.06, what is the probability that the
string of lightbulbs will fail during time period T?
A.0.06
B.(0.06)^10
C.1-(0.06)^10
D.(0.94)^10
E.1-(0.94)^10

A

What if the questions was the probability of failing during the time period T is 0.06 for 9 of the lightbulbs and 0.05 for the 10th lightbulb what is the probablility that the string will fail during time period T
=
(0.06(9) + 0.05)/10

_________________

-talent is the desire to practice-

Director
Joined: 01 Apr 2008
Posts: 827
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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05 Jul 2009, 07:47
Lets get some posts before I post OA.
CEO
Joined: 17 Nov 2007
Posts: 3484
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40

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05 Jul 2009, 08:47
E

1) the probability of not failing for one bulb: 1 - 0.06 =0.94
2) the probability of not failing for 10 bulbs: 0.94^10
3) the probability of failing for the string of 10 bulbs): 1 - 0.94^10
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Manager
Joined: 12 Apr 2009
Posts: 198

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05 Jul 2009, 09:40
nightwing79 wrote:
Economist wrote:
A string of 10 lightbulbs is wired in such a way that if
any individual lightbulb fails, the entire string fails. If for
each individual lightbulb the probability of failing during
time period T id 0.06, what is the probability that the
string of lightbulbs will fail during time period T?
A.0.06
B.(0.06)^10
C.1-(0.06)^10
D.(0.94)^10
E.1-(0.94)^10

A

walker is right.

E it should be.
failing during the time period T is 0.06 for 9 of the lightbulbs and 0.05 for the 10th lightbulb what is the probablility that the string will fail during time period T
=
(0.06(9) + 0.05)/10

walker is right.

E it should be. silly silly.
_________________

-talent is the desire to practice-

CEO
Joined: 17 Nov 2007
Posts: 3484
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40

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05 Jul 2009, 11:45
nightwing79 wrote:
walker is right.

E it should be. silly silly.

silly mistakes is a main reason why I got 50 instead of 51 in Quant.....tricky GMAT

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: String of bulbs   [#permalink] 05 Jul 2009, 11:45
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# String of bulbs

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