Permutation and Combination – Concept and Problems

Important Info

Today I’m going to discuss a very important topic for ibps or other bank exams i.e. permutation and combination. This is primarily because various questions from this section tests candidate’s analytical skill. This topic just involves basic calculations.

Permutation implies arrangement where order of things is important and includes word formation, number formation, circular permutation etc. Combination means selection where order is not important and it involves selection of team, forming geometrical figures, distribution of things etc.

Factorial = Factorial are defined for natural numbers, not for negative numbers.

n! = n.(n-1).(n-2)………3.2.1

For example: 1) 4! = = 24
2) 6!/ 4! = (6.5.4!)/ 4! = 6.5 = 30
3) 0! = 1

Implies Arrangement  Implies Selection
Order of things is important Order of things is NOT important 
Permutation of three things a, b and c taking two at a time are ab, ba, ac, ca,bc and cb (Order is important). 
Combination of three things a,b and c taking two at a time are ab, ca and cb (Order is not important). 
nPr= n!/ (n-r)!  nCr = n!/ (n-r)! r! 
nPn = n!  nCn = 1 
nP0 = 1  nC0 = 1

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