Lesson 14

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 1,000 and help students develop fluency. When students consider the addends carefully and adjust them to facilitate addition (such as by subtracting from one and adding to the other), they practice looking for and making use of structure (MP7).

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• “How do you decide how much to add to one addend and take away from the other addend?”

The purpose of this activity is for students to consider numbers that make sense in situations involving elapsed time. Then students solve the problems. While a variety of times and answers make sense for each situation, students focus on justifying why their choices make sense to them (MP3).

Consider preparing and displaying images of roller coasters and Ferris wheels for students who may be unfamiliar with carnival attractions.

• Groups of 3
• “What are some rides that you might see at a fair or a carnival?”
• “What are some situations at a carnival that could involve time?” (Time spent waiting in line for a ride or waiting for someone. Time spent on a ride. Opening or closing times.)
• 30 seconds: quiet think time
• Share responses.
• “Here are some problems about time at the carnival. They are missing some information.”
• “Each person in your group is going to think of numbers or times that make sense in one of the situations. Explain your choices to your group and work together to solve all three problems.”
• “Decide which problem each member of your group will work on.”

• 1 minute: independent work time
• 8–10 minutes: group work time
• Monitor for different number choices and justifications.

If students say they aren't sure what numbers or times to choose, consider asking:

• “What is the problem about?”
• “How long do you think it would make sense to wait in line (or wait for a friend, or go on rides without breaks)? What time do you think would make sense to arrive at the fair (or to be in line for a ride)?”

• Select 2–3 students to share the numbers they chose for each problem.
• As students share, ask:
  • “How did you decide what numbers (or times) to choose for each problem?”
• Ask the class:
  • “Why do these numbers (or times) make sense for this situation?”
  • “What numbers (or times) would not make sense in this situation?”

The purpose of this activity is for students to write a question that could be answered by given mathematical work and that would make sense in the given situation. When students interpret given student work in terms of the supplied information and decide what question the work might answer, they identify important quantities and their relationships in context (MP4).

• Groups of 2
• “Clare and Tyler took a break at the lemonade stand. Here’s what it might look like.”
• Display the image.
• “What do you notice? What do you wonder?” (Students may notice: The stand is close to the carnival. There are lemons hanging in baskets. Students may wonder: How much lemonade do they make each day? What size can you buy? How much does the lemonade cost?)
• 1 minute: quiet think time
• Share and record responses.

• Read the information about the lemonade stand as a class.
• “What mathematical questions could we ask about this situation?”
• 1–2 minutes: partner discussion
• Share and record responses.
• “Now, look at the mathematical work in each problem. Work with your partner to write a question that could be answered by that work.”
• 5–7 minutes: partner work time
• Monitor for groups that accurately write questions that the work could represent.

If students don’t write a question that could be solved with the given work, consider asking:

• “What numbers from the work do you see in the information about the lemonade stand?”
• “What would the work represent in the lemonade stand situation? What question would lead up to this work?”

• For each problem, invite a group to read the question they wrote.
• Ask the class:
  • “How does their question make sense with this mathematical work and what we know about the situation?”
• Consider asking:
  • “What did you like about writing the questions to match the mathematical work?”
  • “What was challenging about writing the questions to match the mathematical work?”