Monday, October 24, 2011

Unlocking the Keys to Simple Addition

Math might come pretty easily to my son but that doesn’t mean he doesn’t need the practice. There are two main principles that guided the creation of this activity; I wanted:
  • to make a math game that could be changed with more difficult problems as my son’s proficiency grows.
  • a way that he could check his answers independently.

The result was Lock-and-Key Math.

You need 4 supplies for this activity:
Cardstock (print my 4-page PDF on it)
Thirteen 3” x 4” toploading trading card sleeves
dry-erase marker

Cut out the gray key silhouettes. Cut out each of the keys (yes, it’s a pain, but TOTALLY worth it). Take the keys to an office/copy shop to be laminated. Use thick lamination sheets and space the keys widely. Once laminated, line up the keys with each corresponding silhouette, using them as a guide for where to cut the lamination so the final result is a rectangle shape with the key floating inside it.
Put the silhouettes (or locks) inside the thirteen trading-card sleeves. Add addition problems to the keys with a fine-tip dry-erase marker. On the back of each key’s corresponding lock, write the answer on the sleeve with the marker.

Before my son played the Lock-and-Key Math game, we read Loreen Leedy’s Mission Addition. (I love Leedy’s books.) Because the book explains how to add numbers when they are stacked vertically (as opposed to 3 + 4 =), all the Lock-and-Key problems were written that way.

It’s time to play!

I put all the keys is a jumbled pile on the table and laid the locks face-down so the answers were visible. One by one my son picked a key, solved the addition problem, and found the sleeve with the answer. Then he flipped over the sleeve and slid the key into the lock. If he was right, the silhouette matched the key perfectly.

My son patiently and quietly worked through all 13 problems, matching each key to its respective lock. While I planned for him to play the game independently, I failed to consider how excited he’d be with each correct match!


  1. Very cute idea! The kids love self-correcting work. Thanks for sharing the PDFs.

  2. This is a great idea. I'm a maths coordinator in an English school and I'm going to share it with my colleagues.

  3. love this idea - now following

    would love it if you could share this on my link party - Serenity Saturday - at

    Natasha xx

  4. This is very clever. We also love Loreen Leedy math books here.

  5. What a clever idea! I know your 1st grader's teacher might like this one for a center activity.

  6. You have such clever ideas! WOW! I LOVE it!! I think we want to come to your school =-)
    I would love for you to link up at Living Life Intentionally’s Linky party - ~Beth

  7. You seriously have the best ideas. I have bookmarked so many of your posts now :)

  8. Very creative. Can't wait to try this with my daughters!

  9. wow, really inventive! thanks so much for sharing on Craft Schooling Sunday!

  10. Thanks for the printable! I loved your keys so much that I had to use them for my daughter! I just added a twist and made the activity more age appropriate. I've linked back to you here

  11. Thanks for sharing the printable! We loved it very much. Here's the video of my son playing with it:-)