Question:

If n is an integer between 0 and 21, then the minimum value of $n ! (21 - n) !$ is

Updated On: Jul 6, 2022
  • $9 ! 12 !$
  • $10 ! 11 !$
  • $20!$
  • 21 !
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The Correct Option is B

Solution and Explanation

Clearly $10 \left|11\right|$ is the minimum out of the four. $[\because\, 9\left|12\right|=9$ $\left|12\left(11\right)1>\left(9\right)\right|\left(10\right)\left(11\right)|$ $=\left(10\right)!\left(11\right)!]$
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Concepts Used:

Permutations and Combinations

Permutation:

Permutation is the method or the act of arranging members of a set into an order or a sequence. 

  • In the process of rearranging the numbers, subsets of sets are created to determine all possible arrangement sequences of a single data point. 
  • A permutation is used in many events of daily life. It is used for a list of data where the data order matters.

Combination:

Combination is the method of forming subsets by selecting data from a larger set in a way that the selection order does not matter.

  • Combination refers to the combination of about n things taken k at a time without any repetition.
  • The combination is used for a group of data where the order of data does not matter.