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# Permutation Combination Questions and Answers

**Practice Questions on Permutation and Combination**

** Permutation** is explained as the series of r terms that can be completed out of total n number of things. Permutations are often represented by nPr which is equivalent to \frac{n!}{(n – r)!}

The various arrangement of a particular number of undertakings by assuming either few or whole at once is known as permutations. All permutations are prepared with the terms p, q, and r by compelling two at a time, they are formed as PQ, QP, pr, RP, QR, and RQ. The permutations compelled with the terms p, q and r taking all at once are:

pqr, prq, qpr, qrp, rpq, rqp.

** Combination** is explained as selecting r series that can be finished out of total n events. It is signified by nCr that sequentially is equivalent to \frac{n!}{r!(n-r)!}

On the basis of the basic Principle of Counting, when we are able to do a precise series in m ways as well as any additional event in assuming n ways, thus it can be supposed that:

Any one of the taken two activities can be accomplished in m + n means plus,

Two of them are able to be done in m * n ways.

Below are the **Practice Questions on Permutation and Combination**

**Rules **

- There are certain rules that are specified for permutation and combinations. These rules contains formulas and basic know-hows which needs to be considered while solving questions related to the same. It will help you to understand the concept in a better way and to avoid mistakes in the future. To through the below given rules and formulas for gaining further understanding on the subject:
- The number of all combinations of n things, taken r at a time is:

^{n}C_{r} = n! = n (n – 1) (n – 2) … to r factors.

\frac{(n!)}{(n – r)! r!} - While solving question on combinations, you should know the below mentioned formulas:

o ^{n}C_{n} = 1 \text{ and } ^{n}C_{0} = 1

o ^{n}C_{r} = ^{n}C_{(n – r)} - The permutation of n events, taken r at a time, is represented as:

^{n}P_{r} = n(n – 1)(n – 2) … (n – r + 1) = \frac{n!}{(n – r)!} - Key point to know is that the statement questions are chiefly made to check your knowledge to make an equation and then put formulae for it.
- Permutations are used when an issue calls for the number of activities of things as well as various tips are to be calculated.
- Combinations are used when an issue arise for the number of tricks of choosing things along with the order of choice is not to be calculated.