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.
Code: FLASK OC .
F : Fathima Beevi .
First woman judge in supreme court.
L : Leela seth .
First woman chief justice in High court.
A : Annachandy .
First woman judge in High court.
S : Sujatha Manohar .
First woman chief justice in Kerala High court.
K : K.K usha .
First malayali woman to become chief justice in Kerala high court.
O : Omana Kunhamma .
First lady magistrate in India.
C : Cornilia Sorabji .
First woman advocate in India.
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Shortcut tricks on boats and streams are one of the most important topics in exams. These are the formulas and examples on Boats and Streams (Cyclist and the wind or Swimmer and stream) questions. These examples will help you to better understand shortcut tricks on boats and streams questions.
There are multiple types of questions asked from these topics. The speed of the boat in still water and the speed of stream will give in questions, You have to find the time taken by boat to go upstream and downstream. .
The speed of the boat in up and down stream will give in question, you need to find the average speed of the boat.
The speed of boat to go up or down the stream will give in question, you need to find speed of boat in still water and speed of stream.
The time taken by boat to reach a place in up and downstream will given in question, you need to find the distance to the place.
LINE_F...
Suppose there are n people in the party. The first person shakes hand with the other (n-1) guests. The second guest shakes hand with the other (n-2) guests. this will continue until the (n-1) th guest shakes hand with the nth guest.
Total number of handshakes is (n-1) + (n-2).. + 3 + 2 + 1. .
= ((n-1)(n))/2 .
For example, 6 people in a party shake hand with other guests. So how many handshakes will be there?.
=((6-1)(6))/2.
=15.
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