Combinations and Permutations Combinations and Permutations


Combinations and PermutationsCombinations and Permutations



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Permutation and combination related questions are common in PSC and Bank exams.

Before going to Combinations and Permutations, first lean about factorial.

If \'n\' is a positive integer then, factorial of n is denoted as n!.


5! = ( 1 x 2 x 3 x 4 x 5 ) = 120

4! = (1 x 2 x 3 x 4 ) = 24


Permutations are for lists of items, whose order matters and combinations are for group of items where order doesn’t matter. in other words,

  • When the order of items doesn\'t matter, it is called as Combination.
  • When the order of items does matter it is called as Permutation.


The number of permutations of n objects taken r at a time is determined by using this formula:

P(n,r)=n!/(n−r)!

Permutation: Listing your 3 favourite football team in order, from list of 10 teams. P(10,3) = 720.


The number of combinations of n objects taken r at a time is determined by using this formula:

C(n,r)=n!/((n−r)!r!)

Combination: Picking a team of 3 people from a football coaching group of 10. C(10,3) = 10!(3!(10−3)!) = 120.

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Nobel Prize Winners 2020

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The Royal Swedish Academy of Sciences has decided to award the 2020  Nobel Prize in Physics with one half to Roger Penrose and the other half jointly to Reinhard Genzel and Andrea Ghez. Half of the Nobel prize went to Roger Penrose for the "discovery that black hole formation is a robust prediction of the general theory of relativity”, and the other half went to Reinhard Genzel and Andrea Ghez for the "discovery of a supermassive compact object at the centre of our galaxy”,  .

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