How do you distinguish between whether should use a permutation and a combination for a given problem?
1 Answer
Jul 5, 2015
Permutation involves arrangements whereas combination implies number of selections or combinations.
Number of permutations of three letters from given five letters a, b, c, d, e is 60 as follows
abc,acb,bac,bca,cab,cba
abd,adb,bad,bda,dab,dba
abe,...
acd,..
ace,...
ade,...
bcd,..
bce,...
bde,...
cde,...
10 x 6 = 60
now number of combinations of five letters a,b,c,d,e taken three at a time is just ten, namely
abc,abd,abe,acd, ace,ade, bcd,bce, bde, cde.
