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NDA 2016 Maths · Mathematics · Permutations and Combinations · medium

The number of arrangements of the letters of the word ROUTE in which all the vowels are together is

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The number of arrangements of the letters of the word ROUTE in which all the vowels are together is
  1. A. 3636
  2. B. 7272
  3. C. 2424
  4. D. 1212
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Answer: (A) 3636

Treat the three vowels O, U, E as one block. The block and the consonants R and T make 3 objects, arranged in 3!=63!=6 ways. The vowels can be permuted inside the block in 3!=63!=6 ways. Hence the total is 6×6=366\times6=36. Forgetting the internal arrangement gives 6, and 5!=1205!=120 ignores the condition.
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