1
Q
Permutation
A
Order ✓
Num syst
Arrangements words
Prize distribution
2
Q
Combination
A
Hand shake
Team formation
Committee formation
3
Q
Npr
A
Ncr*r!
n!/(n-r)!
4
Q
Ncr
A
n!/(n-r)!r!
Nc(n-r)
5
Q
Arrangements
A
N!
6
Q
Word problem
A
Total no. of words/repeated no!)*
7
Q
Vowel
A
Consider all vowel as one
Ncr=n/r *(n-1)C(r-1)
8
Q
Circular arrangements
A
(N-1)!
9
Q
Nacklace
A
(N-1)!/2
10
Q
Dearrangment
A
Dn = n![1/2! - 1/3! +1/4!….. 1/n!)
11
Q
Committee formation
A
Ncr* Ncr
12
Q
Collinear points
A
Nc2- Rc2+1
13
Q
Triangle
A
Nc3-Rc3
14
Q
Diagonal
A
Nc2-N
15
Q
Counting square
A
1^2+2^2+……..+n^2
16
Q
Rectangle
A
Nc2*Rc2
N- horizontal
R- vertical
17
Q
Handshake
A
[N(n-1)] / 2
Or Nc2
