# The number of words,

Question:

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 alike, is__________.

Solution:

$S \rightarrow 2, L \rightarrow 2, A, B, Y, U$

$\therefore$ Required number of ways $={ }^{2} C_{1} \times{ }^{5} C_{2} \times \frac{4 !}{2 !}=240$