Permutation
for the permutation we first need to understand factorial. n!(read as n factorial)=n(n-1)!=n(n-1)(n-2)!= n(n-1)(n-2)(n-3)! in simple words n factorial is the multiplication of all previous numbers. for example: n=5 n!=5!=5*4*3*2*1=120 rules of factorial: 0!=1 1!=1 Permutation Permutation is an arrangement of things or characters or digits or anything which we have. In simple words, permutation is a number of arrangements that a number of things can have. Formula to find permutations: P(n,r) = npr = n!/(n-r)! { Here, n!=n(n-1)!=n(n-1)(n-2)!=n(n-1)(n-2)(n-3)!} rules to calculate permutation: P(n,0)=nPo=1 P(n,1)=nP1=n P(n,n-1)=nP(n-1)=n For example: What are the different arrangements possible for the first 5 digits when we need only 4 digits at a time. 5P4=5!/4!=(5×4!)/(4!)=5 1. How many words can be made from the first 10 alphabets(capital) of lengh 6? solution: Here n=10 r=6 Total words from the alphabets are: 10P6=10!/6!=10×9×8×7×6!/7!= How many permutations are possible for 4 alp