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A leather pouch contains 10 light bulbs, two of which are de : Quantitative Comparison Questions

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Re: A leather pouch contains 10 light bulbs, two of which are de [#permalink]
Carcass sir, why we are not taking permutation here?
D.B = defective , non-defective

A) D.B , D.B thus (2C1/10C1 * 1C1/9C1) * 2!/2!

B) D.B , D.B , ND.B = 2C1/10C1 * 1C1/9C1 * 8C1/8C1 * 3!/2!
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Re: A leather pouch contains 10 light bulbs, two of which are de [#permalink]
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Sir this is a probaility question

Probability is the measure of the chance of occurrence of a future event. It tells us how likely we expect the event to happen.


permutation and combination are different things

1. Each of the different orders of arrangements, obtained by taking some, or all, of a number of things, respective of the order in which the things appear in the group, is called a Permutation.

2. Each of the different groups, or collections, that can be formed by taking some, or all, of a number of things, irrespective of the order in which the things appear in the group, is called a Combination.


See here on probability https://gre.myprepclub.com/forum/gre-pr ... tml#p83091

here on permutation and combination https://gre.myprepclub.com/forum/gre-pe ... tml#p83002
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Re: A leather pouch contains 10 light bulbs, two of which are de [#permalink]
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Carcass sir, Understood i oversight "THEN" in quantity B which states a specific order thus no need of permutation.

A) D.B , D.B thus (2/10 * 1/9) * 2!/2! = 1/45

B) D.B , D.B , ND.B = 2/10 * 1/9 * 8/8 =1/45

thus C
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Re: A leather pouch contains 10 light bulbs, two of which are de [#permalink]
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