Sum

How many 4 letter words can be formed using letters in the word MADHURI if letters cannot be repeated

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#### Solution

There are 7 different letters in the word 'MADHURI' and we have to form 4-letter words.

i.e., n = 7 and r = 4

If the repetition of letters is not allowed, then the number of 4-letter words

= ^{n}P_{r} = ^{7}P_{4}

= `(7!)/((7 - 4)!)`

= `(7!)/(3!)`

= `(7 xx 6 xx 5 xx 4 xx 3!)/(3!)`

= 840.

Concept: Concept of Permutations - Permutations When Some Objects Are Identical

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