Combination is basically called as a selection where order does not matters.Here we need to arrange the digits , numbers , alphabets, colors and letters taking some or all at a time. It is represented as nCr.
- nCr = n!/ r! × (n-r)!
- nC0 = 1
- nCn = 1
- nCr = nCn - r
- nCa = nCb => a = b => a+b = n.
- nC0 + nC1+ nC2+ nC3+ ...............+ nCn = 2n
Permutation vs Combination
In both the things main difference is of order .In permutation order matters while in combination it does not.
Basic Difference :
- arrange or choose
- number of permutation > number of combination