In how many different ways can the letters of the word 'RUMOUR' be arranged?
The word 'RUMOUR' has 6 letters.
In these 6 letters, 'R' occurs 2 times, 'U' occurs 2 times and rest of the letters are different.
Hence, number of ways to arrange these letters
=$\dfrac{6!}{\left(2!\right)\left(2!\right)}$
=$\dfrac{6\times5\times4\times3\times2\times1}{\left(2\times1\right)\left(2\times1\right)}$
=180