Question

Local phone numbers consist of seven numerals, the first three of which are common to many users. A small town's phone numbers all start with 313, 359, or 387. How many phone numbers are available?

Answer 1

Answer:

30,000 phone numbers.

Step-by-step explanation:

If the first three numbers are already defined then it means that only the other 4 digits remain to be defined.

The solution would be the number of numbers between 0000 and 9999, because the order here matters, since each number is different.

Therefore between these two numbers there are a total of 10,000 numbers, that is to say that for each of the three initial numbers there are 10,000 numbers, therefore in the town there are a total of 30,000 numbers.