In how many different ways can the letters of the word DRASTIC be arranged in such a way that the vowels always come together ?
There are 7 letters in the word 'DRASTIC' including 2 vowels (A,I) and 5 consonants (D,R,S,T,C).
Considering the two vowels as 1 letter, we have 6 letters which can be arranged in 6! ways
But corresponding to each way of these arrangements, the vowels can be put together in 2! ways.
Hence, required number of words = $$6! \times 2!$$
= 720 * 2 = 1440
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