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.
P - Principal, the sum of money lent or borrowed. .
R - Rate of interest: Annual interest, often expressed as a percentage. .
T - Time period for which the money is lent or borrowed. .
Simple Interest = Principal * Time * Rate of interest / 100 .
SI = 4000× 8% × 4 = 4000× 0.08 × 4.
= 1280. .
In compound interest , the principal amount with interest after the first time period becomes the part of principal for the next time period.
CI = [P (1 + R/100)^T] – P .
Total amount = [P (1 + R/100)^T] .
If time period is half-yearly, .
Amount = P[1 + (R/2)/100]^2T .
If time period is quarterly, .
Amount = P[1 + (R/4)/100...
What is the divisibility by 2 Rule?.
Even numbers are multiples of 2. A number is even if ends in 0,2,4,6, or 8.
What is the divisibility by 3 rule?.
A number is divisible by 3 if the sum of its digits is divisible by 3.
372, for instance, is divisible by 3 since sum of its digits (3+7+2) is 12. And 12 is divisible by 3.
What is the divisibility by 4 rule?.
A number is divisible by 4 if the number\'s last two digits are divisible by 4.
9,312, for instance, is divisible by 4 since its last 2 digits are 12. And 12 is divisible by 4.
What is the divisibility by 5 rule?.
A number is divisible by 5 if its last digit is a 0 or 5.
What is the divisibility by 6 rule?.
Since 6 is a multiple of 2 and 3, the rules for divisibility by 6 are a combination of the rule for 2 and the rule for 3.
Divisibility by 8 Rule.
A number passes the test for 8 if the las...
Code -“BHAJI SABJI FOR MAASAAB”.
B : Babur.
H : Humayun.
A : Akbar.
JI : Jahangir.
S : Shah jahan.
A : Aurangazeb.
B : Bahadur shah.
JI : Jahandar shah.
For : Farrukhsiyar.
M : Muhammad Shah.
A : Ahmad Shah.
A : Alamgir II.
SA : Shah Alam II.
A : Akbar II.
B : Bahadur Shah Zafar.
...
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