SOLUTION: Suppose any 7-digit number whose first digit is neither 0 nor 1 can be used as a telephone number. a. How many telephone numbers are possible if repetition of digits is allo

Question 1065677: Suppose any 7-digit number whose first digit is neither 0 nor 1 can be used as a telephone number.
a. How many telephone numbers are possible if repetition of digits is allowed? b. How many are possible if repetition of digits is not allowed?
c. A number such as 911-_ _ _ _ �WASTES� a lot of phone numbers. How many phone total numbers are wasted due to 911, 411 & 555?
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
a)
b)
c) Well wasted is kind of subjective, you lose 10000 numbers for each 3 digit special prefix (assuming repetition,
or 50400 without repetition). So 30000 lines wasted just to have potentially lifesaving response.
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