Chapter 9, Problem 87RE

To determine

To Find:How many different telephones numbers are possible by changing only the last four digits.

Answer to Problem 87RE

  $10,000$

Explanation of Solution

Given:All the landline telephone number in aa small town use the same three digit prefix.

Since we have to change the only last four digits of the number

The first number has the $10$ possibilities as well as the next $3$

i.e.

Number of different telephones numbers are possible by changing only the last four digits is

  $10\times 10\times 10\times 10=10,000$

Hence, $10,000$ ways