Lesson 11
Add to a Teen Number
Warmup: True or False: Teen Numbers (10 minutes)
Narrative
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 equation.
Student Facing
Be prepared to explain your reasoning.
 \(10 + 4 = 10 + 5\)
 \(10 + 3 = 2 + 1 + 10\)
 \(14 = 10 + 4 + 5\)
Student Response
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Activity Synthesis
 “Does anyone want to add on to _____ ’s reasoning?”
 “Did you determine if any of these were true or false without solving? How?” (I knew the first one without solving. Both had 10 + something, and one had a 4 and one had a 5, so they are not equal.)
Activity 1: Rock Collection (10 minutes)
Narrative
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give each group access to double 10frames and connecting cubes or twocolor counters.
 “Something that is common for people to collect is rocks. People collects lots of different types of rocks. We are going to solve a problem about a rock collection.”
Activity
 Read the task statement.
 3 minutes: independent work time
 “Share your thinking with your partner.”
 2 minutes: partner work time
 Monitor for students who represent their thinking using 10frames to show 14 and then add 3 more.
Student Facing
Kiran collects rocks.
So far he has 14 rocks.
He goes on a hike and collects 3 more rocks.
How many rocks does Kiran have?
Show your thinking using drawings, numbers, or words.
Equation: ________________________________
Student Response
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Activity Synthesis
 Invite previously identified students to share.
 “How did the representation change when they added three ones? What stayed the same?” (You start with a full 10frame and four ones, and when you add three more, that 10frame does not change. This 10frame changed because now there are four red counters and three yellow counters.)
Activity 2: Write Equations: Adding on to Teen Numbers (10 minutes)
Narrative
The purpose of this activity is for students to add a onedigit number to a teen number. All of the totals are within 20. Students are provided 10frames and twocolor counters which they may choose to use to represent the sums. Using 10frames encourages students to see that the unit of ten stays the same and the ones are combined.
During the activity synthesis, the teacher records how students found the value of the sum of \(17 +2\). It is important that the teacher write the equation the way that students think about the answer to the problem. For example, the equation \(17 + 2 = \boxed{19}\) represents students who show 17 counters and count on as they add two more. The equation \(7 + 2 + 10 = \boxed{19}\) or \(10+7 + 2 = \boxed{19}\) represents students who see that the ten stays the same and they can add the ones to help them find the total.
Advances: Representing, Conversing
Supports accessibility for: Attention, SocialEmotional Functioning
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give students access to double 10frames and connecting cubes or twocolor counters.
Activity
 Read the task statement.
 5 minutes: independent work time
 2 minutes: partner discussion
 Monitor for students who find the value of the sum \(17 + 2\) in these ways:
 \(17 + 2 = \boxed{19}\)
 \( 7 + 2 + 10 = \boxed{19}\)
Student Facing
Show your thinking using drawings, numbers, or words.

\(12 + 5 = \boxed{\phantom{\frac{aaai}{aaai}}}\)

\(6 + 11 = \boxed{\phantom{\frac{aaai}{aaai}}}\)

\(\boxed{\phantom{\frac{aaai}{aaai}}} = 17 + 2\)

\(4 + 14 = \boxed{\phantom{\frac{aaai}{aaai}}}\)

\(\boxed{\phantom{\frac{aaai}{aaai}}} = 15 + 4\)
 \(16 + 2 = \boxed{\phantom{\frac{aaai}{aaai}}}\)
Student Response
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Activity Synthesis
 Display each missing number.
 Invite previously identified students to share.
 “How does \(17 + 2 = \boxed{19}\) match _____’s work?” (They put 17 on and then counted 2 more—18, 19—to get the value.)
 “How does \( 7 + 2 + 10 = \boxed{19}\) match _____’s work?” (They added the ones and got 9 and then added 10 to get 19.)
Activity 3: Centers: Choice Time (20 minutes)
Narrative
The purpose of this activity is for students to choose from activities that offer practice adding and subtracting within 10. Students choose from previously introduced centers.
 Compare
 Number Puzzles
 Find the Pair
Required Materials
Materials to Gather
Required Preparation
 Gather materials from previous centers:
 Compare, Stage 1
 Number Puzzles, Stage 1
 Find the Pair, Stage 2
Launch
 Groups of 2
 “Now you are going to choose from centers we have already learned.”
 Display the center choices in the student book.
 “Think about what you would like to do first.”
 30 seconds: quiet think time
Activity
 Invite students to work at the center of their choice.
 8 minutes: center work time
 “Choose what you would like to do next.”
 8 minutes: center work time
Student Facing
Choose a center.
Compare
Number Puzzles
Find the Pair
Activity Synthesis
 “How do you choose which center will be most helpful for you?”
Lesson Synthesis
Lesson Synthesis
Display \(\boxed{20} = 18 + 2\) and the double 10frame representation.
“Today we added to teen numbers. What are different ways to find the value that makes the equation true?” (I can count up 19, 20, I can add the ones, so \(8 + 2 = 10\) and then \(10 + 10 = 20\), I can put 2 more in my 10frames and see that both are filled, which is 20.)
Write equations to represent each student’s thinking.
Cooldown: Unit 3, Section B Checkpoint (0 minutes)
CoolDown
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