How many ways are there to arrange the letters in the word ADDRESS if the two Ds must be together?

Answer 1

The permutations of the letters ADDRESS if the two D's must be together is the same as the permutations of the letters ADRESS, which is 6 factorial, or 720, divided by 2, to compensate for the two S's, which means that the number of distinct permutations of the letters ADDRESS, where the two DD's must be together is 360.