if 4 consecutive letters are selected at random from the english alphabet , then the probability that one of the letters is a vowel is ?
total no . of ways of selecting 4 consecutive letters = > 23 [ like abcd , bcde , efgh , . . etc ] no . of ways of having one is a vowel = > abcd , bcde , cdef , defg , efgh , fghi , ghij , hijk , ijkl , lmno , mnop , nopq , opqr , rstu , stuv , tuvw , uvwx . . . = 17 p ( one of letter is vowel ) = 17 / 23 answer : d
subtract(const_1, divide(const_6, subtract(const_26, const_3)))