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In order to guarantee all emergency phone calls are received, the phone company wants all phone numbers with a 9 followed by two 1's to be routed to the
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In order to guarantee all emergency phone calls are received, the phone company wants all phone numbers with a 9 followed by two 1's to be routed to the
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Question 585050: Here is a word problem:
In order to guarantee all emergency phone calls are received, the phone company wants all phone numbers with a 9 followed by two 1's to be routed to the 9-1-1 emergency help center. This will ensure that any real emergency victims will still get the help they require regardless of whether or not they accidentally hit extra keys. The digits 9-1-1 do not need to be consecutive but they do need to be in that order (e.g. 197-8141 and 009-1211) would get routed to 9-1-1, but 514-9313 would not, since the 9 is only followed by a single one. How many 7-digit phone numbers would not be able to be used since they would be routed to the 9-1-1 emergency center? Assume all 7-digit phone numbers are available from 000-0000 to 999-9999. Answer by richwmiller(17219) (Show Source):
