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How Many Words, with Or Without Meaning Can Be Formed from the Letters of the Word 'Monday', Assuming that No Letter is Repeated, If (I) 4 Letters Are Used at a Time - Mathematics

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Question

How many words, with or without meaning can be formed from the letters of the word 'MONDAY', assuming that no letter is repeated, if (i) 4 letters are used at a time 

Solution

There are six letters in the word MONDAY.

 4 letters are used at a time:
Four letters can be chosen out of six letters in 6C4 ways.
So, there are 6C4 groups containing four letters that can be arranged in \[4!\]ways.
∴ Number of ways = \[{}^6 C_4 \times 4! = \frac{6!}{4! 2!} \times 4! = \frac{6!}{2!} = 360\]

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Factorial N (N!) Permutations and Combinations
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Chapter 17: Combinations - Exercise 17.3 [Page 23]

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RD Sharma Mathematics [English] Class 11
Chapter 17 Combinations
Exercise 17.3 | Q 3.1 | Page 23

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