How many 5-digit telephone numbers can be constructed using the digits 0–9 if each number starts with **67** and no digit appears more than once?
A$336$
B$560$
C$720$
D$1000$
Answer & Solution
Correct answer: A. $336$
First two digits are fixed as 6, 7. Remaining 3 positions are filled from the 8 unused digits (0, 1, 2, 3, 4, 5, 8, 9) with no repetition: $8 \times 7 \times 6 = 336$.
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