As the students assemble, I place a 3 digit by 3 digit addition problem on the board and ask them to solve with a partner on their white boards. We have been working on strategies to efficiently and accurately solve problems, so I will watch for application of those strategies.
I introduce the term "expanded notation" to the students and ask them to tell me what they think "expanded" means. During this conversation, I listen for phrases and explanations that will help students remember what the term means.
Then I put 300 + 70 + 9 = 379 and ask the students to discuss why that makes sense and how they can use the word "expanded" to their discussion.
Now, I will tell the students that as they explore and solve problems today, they should try to use the strategy of expanding numbers into their values based on the place they are located.
Students need many opportunities to explore and make sense of situations involving more than one step to solve a math problem. Today, my students are given the task of solving the problem 178 + 225 = n. I have asked them to use their understanding of expanding a number in some way to show their work.
This student wrote out both addends in their expanded form and then added the places together.
In this clip, you will see the student paired her current understanding of expanded notation to the model of base 10 blocks. She went on to circle the like blocks and then represented them in her solution.
After allowing the students to share their different solutions at their tables, I remind them that learning to identify efficient strategies, like expanded notation, will help them mentally solve larger math problems.
I will also inform them that tomorrow we will be using only the expanded notation method to solve addition problems.