Chapter 15.5, Problem 2WE

To determine

To calculate: The number of odd 2-digit positive integer greater than 20.

Answer to Problem 2WE

The number of odd 2-digit positive integer greater than 20are $40$ .

Explanation of Solution

Given information:

Odd 2-digit positive integer greater than 20 are to be formed.

Formula used:

Fundamental counting principle states that if there are m ways to make a selection and n ways to make a second selection then there are $m\times n$ number of ways in which two selection can be made.

Calculation:

Consider the provided information that odd 2-digit positive integer greater than 20 are to be computed.

Let odd 2-digit positive integer be $\boxed{}\boxed{}$ .

Odd numbers are 1,3, 5, 7 and 9.

To select the first digit at tenths place, choices are between 2 to 9 any number $\boxed{8}\boxed{}$ .

There are 5 possible options for ones’ digit that is an odd digit $\boxed{8}\boxed{5}$ .

Recall that Fundamental counting principle states that if there are m ways to make a selection and n ways to make a second selection then there are $m\times n$ number of ways in which two selection can be made.

Therefore, the number of ways to select are,

  $8\times 5=40$

Thus, the number of odd 2-digit positive integer greater than 20 are $40$ .