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# A leather pouch contains 10 light bulbs, two of which are de

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Joined: 20 May 2014
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Kudos [?]: 49 [2] , given: 220

A leather pouch contains 10 light bulbs, two of which are de [#permalink]  29 Oct 2017, 01:18
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Question Stats:

68% (00:47) correct 31% (00:24) wrong based on 19 sessions
A leather pouch contains 10 light bulbs, two of which are defective.

 Quantity A Quantity B The probability of drawing two defective light bulbs (without replacement) The probability of drawing two defective light bulbs (without replacement) and then a non-defective bulb

A. The quantity in Column A is greater
B. The quantity in Column B is greater
C. The two quantities are equal
D. The relationship cannot be determined from the information given

Kudos for correct solution.
[Reveal] Spoiler: OA
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Joined: 03 Sep 2017
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Kudos [?]: 330 [1] , given: 66

Re: A leather pouch contains 10 light bulbs, two of which are de [#permalink]  30 Oct 2017, 07:01
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The probability of extracting two defective light bulbs without replacement is equal to $$\frac{2}{10}*\frac{1}{9} = \frac{1}{45}$$.

The probability of extracting two defective light bulbs without replacement and then a non-defective one is equal to $$\frac{2}{10}*\frac{1}{9}*\frac{8}{8} = \frac{1}{45}$$.

The idea is that there are 2 defective light bulbs out of 10 in the first draw, then there is just one out of the 9 light bulbs remained. Once the two defective light bulbs are extracted there are eight out of 8 non defective light bulbs.

The two quantities are equal.

Re: A leather pouch contains 10 light bulbs, two of which are de   [#permalink] 30 Oct 2017, 07:01
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