# Combinations and Permutations

## Combinations and Permutations

Permutation and combination related questions are common in PSC and Bank exams.

Before going to Combinations and Permutations, first lean about factorial.

If n is a positive integer then, factorial of n is denoted as n!.

5! = ( 1 x 2 x 3 x 4 x 5 ) = 120

4! = (1 x 2 x 3 x 4 ) = 24

Permutations are for lists of items, whose order matters and combinations are for group of items where order doesn’t matter. in other words,

• When the order of items doesn\\\'t matter, it is called as Combination.
• When the order of items does matter it is called as Permutation.

The number of permutations of n objects taken r at a time is determined by using this formula:

P(n,r)=n!/(n−r)!

Permutation: Listing your 3 favourite football team in order, from list of 10 teams. P(10,3) = 720.

The number of combinations of n objects taken r at a time is determined by using this formula:

C(n,r)=n!/((n−r)!r!)

Combination: Picking a team of 3 people from a football coaching group of 10. C(10,3) = 10!(3!(10−3)!) = 120.  Ranks in the Army

കരസേനയിലെ റാങ്കുകൾ.  Code: ജലജ മേജർ ജനറലിനോട് ബിയറിനായി കേണു എൽ സി.ക്ക് മേജറിന്റെ ക്യാപ് ലഭിച്ചു. .

1. ജ : ജനറൽ.

2. ലജ : ലഫ്. ജനറൽ.

3. മേജർ ജനറൽ : മേജർ ജനറൽ.

4. ബിയർ : ബ്രിഗേഡിയർ.

5. കേണു : കേണൽ.

6. L. C : ലഫ്.കേണൽ.

7. മേജർ : മേജർ.

8. ക്യാപ് : ക്യാപ്ടൺ.

9. ലഭിച്ചു : ലഫ്റ്റനന്റ്.

ഇന്ത്യൻ കരസേനയുടെ ഗാനം: മേരാ ഭാരത് മഹാൻ.
ഇന്ത്യൻ സായ...

BODMAS Rule

BODMAS is an acronym and it stands for Bracket, Of, Division, Multiplication, Addition and Subtraction. .

This explains the order of operations to solve an expression. According to Bodmas rule, if an expression contains brackets ((), {}, []) we have to first solve/simplify the bracket followed by of (powers and roots etc.), then division , multiplication , addition and subtraction from left to right. .

Example :.

7 + (6 × 52 + 3) =   7 + (6 × 25 + 3).

7 + (150 + 3).

7 + (153).

7 + 153 .

Ans: 160. .

...

Trick to Remember Mughal Emperors

Code -“BHAJI SABJI FOR MAASAAB”.

B : Babur.

H : Humayun.

A : Akbar.

JI : Jahangir.

S : Shah jahan.

A : Aurangazeb.

JI : Jahandar shah.

For : Farrukhsiyar.

A : Alamgir II.

SA : Shah Alam II.

A : Akbar II.

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