### Home > CCA > Chapter 3 > Lesson 3.2.4 > Problem 3-74

3-74.

Are the odd numbers a closed set under addition? Justify your conclusion. Homework Help ✎

A set of numbers is closed under an operation if the operation cannot be used with numbers from the set to get a number not in the set.

Can you add odd numbers together to get a number that is not odd?

Odd numbers are not a closed set under addition. Some examples:

3 + 5 = 8 3 and 5 are odd, 8 is even

7 + 13 = 20 7 and 13 are odd, 20 is even

15 +15 = 30 15 is odd, 30 is even