In Chicago, all the phone numbers start with 312 or 773. How many different phon

Question

In Chicago, all the phone numbers start with 312 or 773. How many different phone numbers are possible? How many of the phone numbers in Part (a) have no repeated digits? Consider the set of all possible functions / from {1, 2,..., 100} rightarrow {1, 2,..., 100}. How many functions are there? How many of those functions are one-to-one? Repeat Part (a) for the set of all possible functions f from {1, 2,..., 100} rightarrow {1, 2,..., 150}. Repeat Part (b) for the set of all possible functions f from {1, 2,..., 100} rightarrow {1, 2...., 150}.

Explanation / Answer

3a) every phone number consists of 10 digits in chicago . in those 3 are fixed and remaining 7 possible numbers

from those we can get 7! ways of different phone numbers = 5040 ways.

phone numbers without repeation is 7 ways.

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