10 books are placed at random in a shelf. The probability that a pair of books will always be together is -  Choose the correct choice from the following choices: A) 1/5 B) 1/3 C) 1/4 D) 118/2 E) 21/4
10 books can be rearranged in 10! ways consider the two books taken as a pair then number of favourable ways of getting these two books together is 9! 2!   Required probability = 1/5   Answer: 1/4
<result>C</result>
10 books are placed at random in a shelf. The probability that a pair of books will always be together is -