Buttons odd and even
![](http://s3.amazonaws.com/illustrativemathematics/images/000/003/160/thumb/1_ab694ef1af95952055de041e1fd2004f.jpg?1398809661)
6 is even.
![](http://s3.amazonaws.com/illustrativemathematics/images/000/003/161/thumb/2_de8a38971a1a7efce2298a65074d6928.jpg?1398809674)
We can write 3+3=6 to show this.
![](http://s3.amazonaws.com/illustrativemathematics/images/000/003/162/small/3_8cd8777fdb8aa604954b5e6f643303d8.jpg?1398809696)
7 is odd.
![](http://s3.amazonaws.com/illustrativemathematics/images/000/003/163/small/4_779f2817d0da9def7e14fcd30305d1f7.jpg?1398809710)
We can write 3+3+1=7 to show this.
Count out 20 buttons.
- Take 8 buttons and count them by twos to determine if there is an even or odd amount. Write an equation showing if it is even or odd.
- Take 13 buttons and count them by twos to determine if there is an even or odd amount. Write an equation showing if it is even or odd.
- Take 18 buttons and count them by twos to determine if there is an even or odd amount. Write an equation showing if it is even or odd.