One of the key emphases in the CCSS is rigor. Students in this lesson apply their understanding of base 10 to help them decompose numbers on the decade into an appropriate number of tens. Because students are encouraged to approach this task using their own strategy, it is also a complex task. Students show a variety of ways to solve, and we discuss how these strategies are alike and different. This prompts students to reflect on their own thinking and then adjust their strategy if another student's makes more sense.
This problem comes on the heels of us finishing up the story, "Birthday Soup" in Little Bear. It is a great read aloud for first graders (appropriate Lexile level AND adorable?! Can't beat it!). If you have never read it, read it to your kids before starting the lesson! This is aligned to RL1.10-this prose is of appropriate complexity for first graders.
Yesterday we figured out that the story problems were “break into 10s” story problems. They were asking us to break a number into groups of 10.We used how we write the number to help us understand how we could break it into 10s.
Using how we write the number to help us figure out how to break it into 10s makes it easier for us to group objects into 10s fast. For example, if Ms. Cole is making stickers into groups of 10, I see that the number 30 has a 3 in the tens place. Right away I know I will have 3 groups of 10.
Objective: Your thinking job today is: How can I use the way I write numbers to help me break a number into groups of 10?
*All images of Little Bear are copyright Maurice Sendak.
Yesterday we solved a problem that said:
The sticker shop has 30 stickers. They put 10 stickers on the strips. How many strips of 10 will they have?
We saw that this story problem wanted us to break a big number into groups of 10. But guess what?! Lots of problems are break 10 problems. Not just sticker problems! (Remind students of hand motion: see Break It Into Tens Hand Motion video for example!)
We will then read a series of story problems. The focus of each is:
Is this a break into 10s problem? What in the problem tells you that?
This discussion is aligned to MP1-make sense of problems. Students practice reading multiple problems and identifying what is happening in each. By comparing the problems, they see that even though they have different objects, they are all being divided into groups of 10.
Present problem: Ms. Cole baked 40 cookies for a class party. She puts 10 cookies on the plates. How many plates will she need?
Partner talk: Is this a break into 10s problem? How do you know?
Student Work Time: I'll give students 7-10 minutes to solve this problem and represent it in their math journals.
I'll chooses 2 strategies to share-a student who used cubes and a student who used the tens place.
I'll draw how a student did the cubes strategy and have the student act out what they did with the 40 cubes.
Structure of number strategy: This strategy discussion is aligned to MP7, Look for and make use of structure. This student uses the structure of number to help her solve a problem where a number is being divided into 10s.
Group A: Intervention
Goals: Students use cubes and lower numbers (write in 20, 30, 40). Push these students to articulate why they are making groups of 10. Push them to also articulate how many tens.
Group B: Right on Track
Goals: Students can articulate why they are breaking into 10s. These students probably use the ten rods. I'll push them to explain WHY they are using the ten rods, and what those rods represent. Numbers in the story problems are on the decade.
Group C: Extension
Goals: Students apply what they understand about the tens place to figure out how many tens and how many leftovers. Numbers in the story problems all have more than 0 in the ones.
See Little Bear Problems.docx for independent practice sheets!
I tell students to share their first problem with their partner and then explain how they solved by showing their strategy.
After share time, celebrate Little Bear's birthday by watching the animated short film of "Birthday Soup"!