[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 ...

[QUOTE=suja84_ibt;205580]More formulae: [b]PROGRESSION: [/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) [b] ARITHMETIC PROGRESSION[/b] 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 ...