How many words can one form by shuffling the letters of the word QUEUE, if Q is always followed by U? The words thus formed need not necessarily have any meaning.

QUEUE has letters Q, U, E, U, E (5 letters; U appears 2 times, E appears 2 times). Total arrangements without restriction = 5!/(2!2!) = 30. We need Q immediately followed by U. Treat 'QU' as one block. Remaining letters: U, E, E plus the QU block = 4 units with E repeated twice and U appearing once outside. Arrangements = 4!/2! = 12. Hence 12 words can be formed.