Chapter 8.5, Problem 21E

(a)

To determine

To find: the number of ZIP codes consisting of five digits.

Answer to Problem 21E

The possible numbers of digit ZIP codes consisting five digits are $100000$ .

Explanation of Solution

Given information:

The U.S postal service launched the Zoning Improvement plan code to streamline the mail delivery system. A ZIP code consists of a five digit sequence of numbers.

Calculation:

First digit can be any one number from 0 to 9.

Second digit can be any one number from 0 to 9.

Third digit can be any one number from 0 to 9.

Fourth digit can be any one number from 0 to 9.

5th digit can be any one number from 0 to 9.

The possible numbers of digit ZIP codes consisting five digits are:

  $\begin{array}{l}=10\times 10\times 10\times 10\times 10\\ =100000\end{array}$

(b)

To determine

To find: the number of ZIP codes consisting of five digits when the first digit is 1 or 2.

Answer to Problem 21E

The possible numbers of digit ZIP codes with first digit 1 or 2 consisting five digits are

  $20000$

Explanation of Solution

Calculation:

Second digit can be any one number from 0 to 9.

Third digit can be any one number from 0 to 9.

Fourth digit can be any one number from 0 to 9.

5th digit can be any one number from 0 to 9.

The possible numbers of digit ZIP codes with first digit 1 or 2 consisting five digits are:

  $\begin{array}{l}=2\times 10\times 10\times 10\times 10\\ =20000\end{array}$