How many possible four digit telephone number extensions can be formed if 0, 8, and 9 are excluded as the first digit?
Thank you for your help!
Thank you for your help!
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i take it that repetitions are allowed, so
7 choices for 1st digit, 10 each for next 3,
ans: 7*10^3 = 7000 <-------
7 choices for 1st digit, 10 each for next 3,
ans: 7*10^3 = 7000 <-------