Question

How many phone numbers are possible for one area code if the first four numbers are 202-1 , in that order , and the last three numbers are 1-7-8 in any order

Answer 1

6 phone numbers are possible for one area code if the first four numbers are 202-1

Solution:

Given that, the first four numbers are 202-1, in that order, and the last three numbers are 1-7-8 in any order  

We have to find how many phone numbers are possible for one area code.

The number of way “n” objects can be arranged is given as n!

Then, we have three places which changes, so we can change these 3 places in 3! ways

$n! = n \times (n - 1)!$

Hence 3! is found as follows:

$3! = 3 \times (3-1)!\\\\3! = 3 \times 2!\\\\3! = 3 \times 2 \times 1 = 6$

So, we have 6 phone numbers possible for one area code.