Permutation

    Cards (3)

    • No. of selection of r things out of n "identical" things is 1
    • No. of permutation of n different things taken r times is n^r
      Example:
      In how many ways 4 rings can be worn in three fingers: 3^4
    • Total number of selections out of n different things: 2^n
      All selections except selection of zero selection: 2^n - 1
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