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: ഇപ്പൊ ഭിക്ഷയ്ക്കു അവിടെ പോഡി .
ഇപ്പൊ ഭി - ഹെപ്പറ്റൈറ്റിസ് ബി .
ക്ഷ - ക്ഷയം .
അ - അഞ്ചാം പനി .
വി - വില്ലൻ ചുമ .
ടെ - ടെറ്റനസ് .
പോ - പോളിയോ .
ഡി - ഡിഫ്ത്തീരിയ.
...
Formula : .
Train Speed = Distance / Time.
Points to Remember .
To change km/hr into m/sec, we need to multiply it by 5 / 18. .
Example:.
90 km/hr means.
90 x 5 / 18.
= (5 x 5 ).
= 25 m/sec.
And if we need to convert m/sec into km/hr, we multiply it by 18 / 5.
Example:.
90 m/sec means.
90 x 18 / 5.
= ( 18 x 18 ).
= 324 km/hr.
Time taken by a train of length l meters to pass a pole or standing man or a signal post is equal to the time taken by the train to cover l meters.
Time taken by a train of length l meters to pass a stationary object of length b meters is the time taken by the train to cover (l + b) meters.
Suppose two trains or two objects bodies are mo...
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. .
...
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