Math Detectives Solve the Mystery of The Missing Addends!

This past week, 1st graders at McDole learned how to find missing addends 
( __+7=12). We put on our detective hats and worked hard to find the missing addend!

1.OA.4 Understand subtraction as an unknown-addend problem.
1.OA.8 Determine the unknown whole number in an addition or subtaction equation.

We started our week by reviewing what an addend and a sum are. We have focused  on using these vocabulary words during our math block. 

Earlier in the school year, we learned that dominoes can help us with addition. If you add the dots on both sides you get the sum. We practiced using dominoes to add and we used this skill to help us find the missing addend. 

Students started by drawing the known addend on one side of the domino. Then, they counted on by added dots on the second half of the domino. They stopped counting when they reached the sum. The last step was to count up how many dots were drawn in the second half of the domino. And then...MYSTERY SOLVED! We found the missing addend. 

 

Students also learned a missing addend game called "What's my number?" Two students come to the front of the room. They act as the addends. It is their job to figure out the number that is stuck to their forehead. They can only see the other addend and the sum (students at their seats write the sum of the two numbers on their white boards). 

Your favorite 1st grade team, 

Mrs. Baker, Mrs. Bright, Miss Gianakakos and Miss Steimel