Thursday, March 29, 2012

Math: Strategy for Adding 3 Numbers and Finding "x"

Common Core Standard: MATH; 1.OA.1 and 2.OA.1

This is a first grade activity but I feel like it fits in 2nd grade as well because there is more than just one step in solving these problems.

My students have pretty much got adding 2 numbers down pat. Now we are starting to work on adding 3 numbers and I wanted an activity that was hands-on, visual, and fun!!

I created a sheet that had the numbers 0-11. I felt like my students would be more comfortable using smaller numbers and they would be able to do the activity with more independence. Each student got with a partner, and I stressed to them to choose their partners wisely:) "Who will you work well with? Who will help you?" I told them that as I walk around and observe that I wanted to hear them communicating as a team so choosing a GOOD partner is VERY important.

I gave every pair a sheet with the numbers.

One person was responsible for cutting the numbers and laying them out

I then told them to flip all of their numbers over, just like they would in a memory game.

They would alternate picking 3 cards at a time.

On their "3 Number Addition" Mat, they had to lay out the 3 numbers in the order they were turned over in the empty boxes, leaving the "sum" box blank.

They had to place a red counter above the 2 largest numbers. This strategy is based on getting them to the answer quickly. I think this basic strategy is a good place to start. Soon, I hope for them to see patterns with the numbers (ways to make 10, doubles, etc) when thinking of quicker ways to get to an answer.

In their Math Journals, they recorded the number sentences and showed the largest numbers by using a red crayon.

I flicked the lights (a good attention getter) and altered the activity after walking around and observing that students were successful with the first part. Now they had to leave one of the addend boxes blank and find "x". We have solved problems in class such as      7 + x = 10.
x = ? so for this activity they had to do the same with 3 numbers. I showed examples on the smart board and we did a few together, then allowed them to work with their partner to come up with more combinations using the numbers they had.

After spending time finding "x", I had them return to their seats and independently write a response to the activity.
"What did you learn? What did you like the most? Explain the steps you and your partner took to get to the answer." 
I think it's very important to allow that time for your students to reflect back on their learning and write about it.

My students loved this activity!! They were engaged, communicating, listening to their partners, and learning from each other. It was a huge success!!

Here are the sheets if you would like to download.
I would enjoy hearing comments!


  1. Thank you for the idea. Changing it up to find one of the addends is a sweet twist!

    ❀ Tammy
    Forever in First

  2. I absolutely LOVE this idea!! Thanks for sharing it.

  3. Used it with my math kiddos today in first grade...They had a blast! I'm going to share your link today on my blog :) You should come check it out.

    1. I'm so glad you gave this a try and your kids liked it!!! It's always nice to hear of others trying out your ideas and it working for them too:) Thanks for sharing it on your blog!!

  4. Thank you, this help my son out!!😁 we have fun with it!

  5. HEY TAMMY!!!!!!!!!!!!! I was looking for a great activity for adding 3 numbers and of course I found one on your blog. I LOVE IT!!! and I miss you so much.


Note for the Teacher