For my activity, I placed subtraction and addition problems on the tops of each with labels (I also included a certain number of points for each one which will be explained later.). This could also be written on with a permanent marker. I write horribly, so labels are great!
Then, on the inside of each cap, I wrote the answer with a Sharpie marker.
All the different, colorful tops that you can find just make the game even more appealing. Here's a sanitizer wipes bottle top:
Here's a shampoo bottle top:
How to Play Answer Keepers:
1) Students can play alone or in groups, since it is self-checking.
2) If playing in groups, place all the bottle caps in a bag. Students needs whiteboards and dry-erase markers or they can record their work.
Click here for the recording sheet.
3) Students each choose a bottle cap (without looking).
4) Students work out the problems on their whiteboards or sheet.
5) Students check their answers by opening the bottle caps and revealing the answers.
6) For correct answers, students mark down the number of points their problems were worth. For incorrect answers, students must return that bottle cap to the bag.
7) Once all bottle cap problems are solved, students add up the points and see who won.
This of course can be done with any kind of problem that has a solution for any grade level. And remember, not only are you teaching students math with this game, you're teaching them to be GREEN! Two lessons in one! :)