Permutation vs. Combination

Permutation vs. Combination

Lessons

- permutation: nPr = number of arrangements of “r” items taken from a set of “n” distinct items (order matters!!) = n!(nr)!\frac{{n!}}{{\left( {n - r} \right)!}}

- combination: nCr = number of selections of “r” items taken from a set of “n” distinct items (order does NOT matter!!) = n!(nr)!r!\frac{{n!}}{{\left( {n - r} \right)!\;\;r!}}
  • 1.
    a) How many ways can two prizes be awarded to a class of 5 students?
    • 1st prize = $100
    • 2nd prize = $5

    b) How many ways can two identical movie tickets be awarded to a class of 5 students?