The number of words, with or without meaning, that can be formed by taking 4 letters at a time from the letters of the word 'SYLLABUS' such that two letters are distinct and two letters are a like, is _________.
The natural number m, for which the coefficient of x in the binomial expansion of
Ans : 13
Four fair dice are thrown independently 27 times. Then the expected number of times, at least two dice show up a three or a five, is _______