മിഷൻ ഇന്ദ്രധനുസ് പദ്ധതിയിൽ ഉൾപ്പെടുന്ന 7 രോഗങ്ങൾ

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! . .


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:.

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. ....

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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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The quickest way to calculate percentages is to multiply numbers first and handle two decimal places later.

For example, 20% of 70 is 20 x 70 = 1400, so the answer is 14. .

70% of 20 is also 14.

To calculate the percentage of 72 or 29, then round up and down to the nearest multiple (70 and 30 respectively) to get a quick approx result.

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