# When to use permutation/combination in a given question of permutation and  combunation?

Permutation:

Each of the arrangements which can be made by taking some or all of a number of things is called a permutation. For example, if there are three objects x, y and z, then the permutations of these objects taking two at a time are xy, xz, yx, yz, zx and zy. In permutation the order of arrangement is taken into account. When the order is changed, a different permutation is obtained. The notation of permutation is given by

Combination:

Each of the different selections made by taking some or all objects irrespective of their arrangement is called combination. For example, if there are three objects x, y and z, then the combinations of these objects taking two at a time are {x,y}, {y,z} and {z,x}. In combination the order of arrangement is not taken into account.

In simple language,

⇒ If the order does matter, it is permutation.

⇒ If the order doesn't matter, it is combination.

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Hai Mayank,

A permutation is an arrangement in a definite order of a number of objects taken some or all at a time.

A combination is the selection of a number of objects taken some or all at a time.

What I want to say is that  if the Q is about selection then combination is used & if the Q is about the arrangement  then permutation is used.

Still if U R not able to understand read page no138 - 139 & 148 - 150 of class11 NCERT textbook. There  these 2 topics with EX have been explained.

Thumps up PLZ.

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