Loading the Bus: Decomposing Teen Numbers

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Objective

SWBAT solve story problems where they decompose numbers 11-19 into ten and some more.

Big Idea

Students have spent time building the numbers 11-19. This lesson gives them the opportunity to go at it from the other direction, taking the numbers and breaking them apart into a ten and some extra.

Setting Up the Learning

5 minutes

CCSS Context:

A key emphasis within the Common Core is on "real world problems". In this lesson, students use excellent children's literature to create a story and solve a problem. The text I chose by Mo Willems is right on level for beginning of the year first graders (RL1.10). This lesson addresses a key base 10 understanding-the special case of the teen numbers (1.NBT.2b). Students use concrete models to decompose a teen number into 10 and some more, all based on a "real" problem-How will Pigeon load these people on the bus?

Review

Yesterday we read “Don’t Let the Pigeon Drive the Bus!” and helped Pigeon load people onto our buses. Today we are going to help Pigeon again, but we are going to help him figure out how many people need to go on each bus. He doesn't know how many buses of 10 he needs!

Connect

Mathematicians have to put objects into groups of 10 to help them solve problems. We are going to be figuring out how many groups of ten are in a number for the rest of the year and even in second grade.

Objective

Your thinking job today is: How can I solve story problems by breaking a number into ten and some more?

 

*All images are copyright of Mo Willems.

Opening Discussion

18 minutes

To start the lesson, I want students to focus on how we built the teen numbers with base ten. Then we will try decomposing them as our new problem for the day.

"Let’s look at one of the problems from yesterday to get us ready to do this thinking job."

Pigeon had 10 people on the bus. Then he loaded 4 more people on the bus. How many people are on the bus?

I'll model how a child used the bus ten frames the day before to solve this problem. 

Guiding Questions:

  • How many people are on the first bus? 10! We see that there is 1 full ten here. 
  • How many extras are there? 4

I'll restate this in mathematical language that they need to be successful with base ten problems later: "We had 14 people and we put them on the buses using 1 full ten and 4 extra people. Look at the number! 14, 1 ten and 4 extras."

Partner Talk for review: How did we put the 14 people on the bus?

I'll present the new problem for the day that students will be trying to solve.

There are 15 people who want to get on the bus. Each bus holds 10 people. How can Pigeon load them on the buses?

Partner Talk: Retell what is happening in this problem.

  •  As I walk around, I'm listening to make sure students don't say that 10 more people got on the bus, but rather that each bus has 10 seats, or holds 10 people. If I hear more than 1 student have that misconception, I'll address it whole group.

I'll highlight how a student retold the problem: "We are starting with 15 people and we need to put them on the buses. How many people will fit on the first bus?" 

Partner Talk for formative data: How many people will be on the second bus? How do you know?

Students may not know how to explain it yet, but some of them will have used strategies to figure it out.

  • Some might use the first problem (14) to help them figure out 15 (I know 15 is just one more)
  • Might count on 10, 11, 12, 13, 14, 15 and keep track on fingers
  • Might use the structure of the number and generalize 14 is 10 and 4 and 15 is 10 and 5

I'll have students work on this problem on their own, using the bus mat ten frames and cubes if they choose to.

Strategies I'll look for during work time (lowest level to highest):

  • Take out 15 cubes, put them on the ten frame (most common)
  • Some might use the first problem (14) to help them figure out 15 (I know 15 is just one more)
  • Might count on 10, 11, 12, 13, 14, 15 and keep track on fingers
  • Might use the structure of the number and generalize 14 is 10 and 4 and 15 is 10 and 5

Strategy Share

10 minutes

I'll bring students back together to share student thinking. My anchor chart will be the bus mat on chart paper along with the problem so we can discuss how the bus mat helped us solve.

I'll choose 2 strategies to share. I'll definitely start with a cubes strategy and then move to one of the other strategies, preferably counting on if a student tries that.

Strategy Share Guiding Questions:

  • How many people fit on the first bus?
  • How many people had to go on the second bus? Why did they have to sit there?
  • How many full tens did we make? How many left over?
  • What do you notice about the number 15? We used 1 ten and 5 left over-look at the number! 1 ten and 5 left over. (Point to the numbers)

If time, I'll follow this sequence again with a different problem, specifically point out the structure of the number. 

Independent Practice

15 minutes

Directions: Students solve problems and write how many full tens and how many extras. Students should use "1 full ten" language to describe how many full buses.

Group A (In need of intervention):

Students definitely should have cubes and the bus mat there to model the problem. Students work with numbers 11-15.

Group B (right on track):

Students use a variety of strategies to figure out how many tens and how many extra. Students may notice that the structure of the number is important, but may not be able to articulate why 14 has a 1 and a 4 in it. If students do not notice this today, it will be focused on more soon. Students work with numbers 11-19. 

Group C (Extension):

These students use a variety of strategies to figure out how many tens and extra but primarily use the structure of the number. They are beginning to understand that the 1 represents a 10. To push these students, I'll start them out without cubes to see if they can solve the problem mentally or using the structure of the number.

Closing

5 minutes

Today’s thinking job was: How can I solve story problems by breaking a number into ten and some more?

I'll lead the students in creating a chart for each of the numbers 11-19 (as many as we have time for) and show them on the buses. I will point out what I am "noticing" about the structure of each number by saying: "When we made 12, we used 1 full ten and 2 extra ones. My number has a 1 first and then a 2!"

I'll post this chart in the class for us to revisit throughout the unit.