# Lesson 12

Saree Silk Stories: Friendship Bracelets

## Warm-up: True or False: Place Value Comparisons (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies and understandings students have for using place value to compare numbers and determine if an equation is true. When students share how they know an equation is true or false based on looking at the total number of tens or total number of ones on each side, they look for and make use of the base-ten structure of numbers and the properties of operations (MP7).

### Launch

•  Display one statement.
• “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time.

### Activity

• Share and record answers and strategy.
• Repeat with each statement.

### Student Facing

Decide if each statement is true or false. Be prepared to explain your reasoning.

• $$24 = 10 + 14$$
• $$15 + 12 = 27$$
• $$26 = 10 + 6 + 10$$
• $$58 = 20 + 20 + 8$$

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• “How can you explain your answer for the last equation using what you know about tens and ones?” (There are only 4 tens on the right.)

## Activity 1: Share Ribbon with Friends (20 minutes)

### Narrative

The purpose of this activity is for students to interpret and solve two-step problems involving length. After reading each story problem, students consider what questions could be asked and what information will be needed in the second part of the problem. Students read each story with a partner, and then solve each story problem independently and compare their solutions.

Students begin the activity by looking at the first problem displayed, rather than in their books. Students represent the problem in a way that makes sense to them and share different representations during the synthesis, explaining how these representations helped solve the problem (MP1, MP2, MP3).

Representation: Access for Perception. Offer strips of colored paper to demonstrate the length of the ribbons, as well as the tape diagrams students create. Encourage students to cut the “ribbon” and label the parts to represent the story. Reiterate the context and connect to the idea of subtraction.
Supports accessibility for: Conceptual Processing, Organization, Memory

### Launch

• Groups of 2
• “The students in Priya’s class are sharing ribbons to make necklaces and bracelets for their friends and family members.”

• Display both parts of the story, but only the problem stems, without revealing the questions.
• “We are going to read this problem 3 times.”
• 1st Read: “Lin found a piece of ribbon that is 92 cm long. She gave Noah a piece that is 35 cm. Then, Lin gave Jada 28 cm of ribbon.”
• “What is this story about?”
• 1 minute: partner discussion
• Listen for and clarify any questions about the context.
• 2nd Read: “Lin found a piece of ribbon that is 92 cm long. She gave Noah a piece that is 35 cm. Then, Lin cut off 28 cm of ribbon for Jada.”
• “Which lengths of ribbon are important to pay attention to in the story?” (length of ribbon Lin started with, length of ribbon given to Noah, length of ribbon given to Jada, length of ribbon Lin has in the end)
• 30 seconds: quiet think time
• 1–2 minutes: partner discussion
• Share and record all quantities.
• Reveal the questions.
• “What are different ways we could represent this problem?” (tape diagram, equations)
• 30 seconds: quiet think time
• 1–2 minutes: partner discussion

### Activity

• “Read the story again with your partner. Then decide how to represent and solve it on your own.”
• “When you have both answered the questions, compare to see if you agree.”
• 10 minutes: partner work time
• Monitor for students who represent each part of the story with:
• tape diagrams
• base-ten diagrams
• other clearly-labeled drawings or diagrams
• equations

### Student Facing

1. Solve. Show your thinking. Use a diagram if it helps. Don’t forget the units.

1. Lin found a piece of ribbon that is 92 cm long. She cut a piece for Noah that is 35 cm. How much ribbon does Lin have left?
2. Then, Lin cut off 28 cm of ribbon for Jada. How much ribbon does Lin have left now?

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• Invite 2–3 previously identified students to display their work side-by-side for all to see.
• “How does each representation help you understand the problem?” (In the diagrams, they used labels to show what each part means. I can see how they used Lin's length of ribbon in both parts. In the equations, I can see the same numbers, but it's a little harder to tell what each part means. I can make sense of them by looking at the other diagrams people made.)

## Activity 2: Friendship Bracelets and Gifts (15 minutes)

### Narrative

The purpose of this activity is for students to represent and solve two-step story problems. The story problems are presented in parts, and students are encouraged to represent each part in a way that makes sense to them. In the synthesis, students compare different ways they represent and solve the problem.

• Groups of 2

### Activity

• 5 minutes: independent work time
• 5 minutes: partner discussion
• Monitor for students who use tape diagrams, base-ten diagrams, and equations to represent each part of the last problem.

### Student Facing

1. Solve. Show your thinking. Don’t forget the units. Use a diagram if it helps.

1. Han has 82 inches of ribbon. He only needs 48 inches. How much should he cut off?

2. Han gives the ribbon he doesn’t need to Clare. Clare uses it to make her ribbon longer. Her ribbon was 27 inches. How long is Clare’s ribbon now?

2. Solve. Show your thinking. Don’t forget the units. Use a diagram if it helps.

1. Andre’s ribbon is too short. He has 28 inches of ribbon, but he needs it to be 50 inches long. How much more ribbon does he need?

2. Andre got the ribbon he needed from Mai. Mai now has 49 inches of ribbon left. How much ribbon did Mai start with?

### Student Response

For access, consult one of our IM Certified Partners.

Students may represent and solve the first part of each problem accurately, but see the second part as a problem with two unknowns. Consider asking:

• “What new information does the second part of the problem give you? What do you need to figure out? What do you already know?”
• “What happened in the first part of the story? What did you figure out? How could you use that in the second part of the problem?”

### Activity Synthesis

• Invite previously identified students to share their diagrams and equations for each part of the problem.
• “How did _____ represent the problem? How does each representation show the story problem?”

## Lesson Synthesis

### Lesson Synthesis

“Today you solved different kinds of story problems that had two parts.”

“How did you represent your thinking and keep track of your calculations? How did you keep up with the lengths you knew and what you needed to find out?” (I used diagrams to make sense of the story. I drew base-ten diagrams to help me solve. I put a circle around my answer so I could use it for the next problem.)

“What ideas for solving story problems have you learned from others?”

Share and record responses.

## Cool-down: Sharing Saree Silk Ribbon (5 minutes)

### Cool-Down

For access, consult one of our IM Certified Partners.

## Student Section Summary

### Student Facing

In this section of the unit, we learned more about standard length units. We measured using inches and feettwo length units from the the U.S. customary system. We also solved two-step story problems about length and interpreted diagrams that represent taking a part away. This diagram shows that we know the length of the ribbon and how much was cut. The question mark represents the length of ribbon that is left.  Han had a piece of ribbon that was 64 inches long. He cut off 28 inches to make a necklace for his sister. How much ribbon is left?