How many permutations of the letters A B C D E F G H consist of string DEF?
Ans: It is the dilemma of finding number of words that can be formed along with the given 8 letters in which DEF come together in that order. There will be six letters to be utilized to form words: A, B, C, DEF, G, H. They can be permuted in 6! = 720 ways. So required number of words is 720.