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  1. Permutations And Combinations

    [QUOTE=suja84_ibt;205994]1. If one operation can be performed in m ways and another operation in n ways, then the two operations in succesion can be done in [b]m*n[/b] ways

    2. The linear permutation of n [b]distinct[/b] objects (that is, the number of ways in which these n objects can be arranged is [b]n![/b] and the circular permutation of n distinct objects is [b](n-1)![/b] But if the clockwise and anticlockwise directions are indistinguishable then the circular permutations of ...
  2. Formulae and Shortcuts - making life easier!

    [QUOTE=suja84_ibt;205580]More formulae:


    [/b]Sum of first n natural numbers: 1 +2 +3 + .... + n = [n(n+1)]/2
    Sum of first n odd numbers: 1 + 3 + 5 + .... upto n terms = n^2
    Sum of first n even numbers: 2 + 4 + 6 + ... upto n terms = n(n+1)

    nth term of an Arithmetic progression = a + (n-1)d
    Sum of n terms in an AP = s = n/2 [2a + (n-1)d]
    where, a is the first term and ...