How many 4-letter codes can be formed using the first 10 letters of the English alphabet, with no letter repeated?
A$5040$
B$1000$
C$10000$
D$40$
Answer & Solution
Correct answer: A. $5040$
$10 \times 9 \times 8 \times 7 = 5040 = {}^{10}P_{4}$.
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