Discussion
The number of three letter words, with or without meaning, which can be formed using letters of the word 'VIRUS' without repetition of letters is
Answer: C
The number of words is 60.
VIRUS has five different letters. A three-letter word without repetition is an ordered arrangement of 3 of them, a permutation:
\[ ^{5}P_{3} = 5 \times 4 \times 3 = 60 \]
30 halves this, and 40 is not a count of arrangements of these letters. 120 is \(5!\), the number of five-letter arrangements. Counting combinations \(\binom{5}{3} = 10\) would ignore order, which words do not.
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