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# If you test 2 different lightbulbs from a box of 100 bulbs that contai

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Math Expert
Joined: 02 Sep 2009
Posts: 58464
If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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30 Oct 2017, 23:59
00:00

Difficulty:

15% (low)

Question Stats:

70% (00:43) correct 30% (01:16) wrong based on 119 sessions

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If you test 2 different lightbulbs from a box of 100 bulbs that contains 1 defective bulb what is the probability that both lightbulbs that you test are defective?

(A) 0
(B) 0.0001
(C) 1/9,900
(D) 0.01
(E) 1/99

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Concentration: Strategy, Finance
GMAT 1: 620 Q46 V29
Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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31 Oct 2017, 07:02
If box contains only 1 defective lightbulb, then the probability that one can pick out 2 different defective lightbulbs is zero.
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Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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31 Oct 2017, 07:15
3
In 100 lightbulbs, only 1 bulb is defective => You never choose 2 bulbs which are both defective. Therefore, probability should be zero.

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Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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31 Oct 2017, 08:23
Bunuel wrote:
If you test 2 different lightbulbs from a box of 100 bulbs that contains 1 defective bulb what is the probability that both lightbulbs that you test are defective?

(A) 0
(B) 0.0001
(C) 1/9,900
(D) 0.01
(E) 1/99

From the highlighted parts it is clear that both Light bulbs can not be defective at the same time, thus answer must be (A) 0
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Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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01 Nov 2017, 17:08
Bunuel wrote:
If you test 2 different lightbulbs from a box of 100 bulbs that contains 1 defective bulb what is the probability that both lightbulbs that you test are defective?

(A) 0
(B) 0.0001
(C) 1/9,900
(D) 0.01
(E) 1/99

Since there is only one defective bulb, the probability of testing two defective bulbs is zero.

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Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai  [#permalink]

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02 Dec 2018, 18:31
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Re: If you test 2 different lightbulbs from a box of 100 bulbs that contai   [#permalink] 02 Dec 2018, 18:31
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