Question 134751
the telephone extensions at a company use 4 digits
a. how many extensions are possible if there no restrictions?
Ans: 10^4 = 10,000
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b. how mant extensions are possible if the first digit cannot be 0 or 9?
Ans: 8*10^3 = 8000
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c. how many extensions are possible if the first digit can only be 1?
Ans: 1*10^3 = 1000
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Cheers,
Stan H.