Question:
Find the number of words formed (may be meaningless) by using all the letters of the word ‘EQUATION’, using each letter exactly once.
Solution:
There are 8 alphabets in the word EQUATION.
Formula:
Number of permutations of $n$ distinct objects among $r$ different places, where repetition is not allowed, is
$P(n, r)=n ! /(n-r) !$
Therefore, a permutation of 8 different objects in 8 places is
$P(8,8)=\frac{8 !}{(8-8) !}=\frac{8 !}{0 !}=\frac{40320}{1}=40320$
Hence there are 40320 words formed.