Class 11th mathematics(permutations and combinations)

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What are Permutation and Combination?

When an event happens in mdifferent ways and another event happened in n different ways, then the total happening number of events is m x n.

Equation of Permutation

If the permutation of a certain number is denoted by n with respect to time t and repetition is not allowed, then the equation is denoted by Pnrand is given by Pnr=n!/(n−r)! and 0≤r≤n
  • The fundamental principle of counting (FPC)
    • Let’s suppose from place A, there are m ways to reach a place B and n ways to reach place C.
    Then by FPC, there are many ways to go from station A to station C
  • The number of permutations of n different things taken r at a time, where p1 is the first kind of objects and p2Are the second kind and son on to k then the equation is represented by
    • n!/p1!p2…p(k)!

Equation of Combination

The definition can be constructed as the number of combinations of n different things taken r in once and is denoted by Cnr and the combination formula is Cnr=n!/r!(n−r)!where 0≤r≤n

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