The purpose of this True or False? is to elicit insights students have about composing teen numbers as a ten and some ones. This will be helpful later in the lesson when students add a single-digit number to a teen number within 20.
Launch
Display one equation.
“Give me a signal when you know whether the statement is true and can explain how you know.”
Decide whether each equation is true or false.
Be prepared to explain your reasoning.
Student Response
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Advancing Student Thinking
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
Standards Alignment
Building On
Addressing
1.OA.A.1
Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.See Glossary, Table 1.
Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., ); decomposing a number leading to a ten (e.g., ); using the relationship between addition and subtraction (e.g., knowing that , one knows ); and creating equivalent but easier or known sums (e.g., adding by creating the known equivalent ).
The purpose of this activity is to elicit and discuss methods for adding a one-digit number to a teen number within 20. Students are presented with a simple story problem type (Add To, Result Unknown) so discussion can focus on the methods students used to find the sum.
Students represent and solve the problem in a way that makes sense to them (MP1). Some students may build the teen number, add counters and count all. Other students may count on from the teen number. Some students may see that the sum will still have 1 ten and just combine the ones. During the Synthesis, students notice that when adding to teen numbers within 20, the unit of ten in the representation does not change—only the ones change (MP8).
Launch
Groups of 2
Give each group access to double 10-frames and connecting cubes or two-color counters.
“Something that is common for people to collect is 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 10-frames to show 14 and then add 3 more.
Kiran collects rocks.
So far, he has 14 rocks.
He gets 3 more.
How many rocks does Kiran have now?
Show your thinking using drawings, numbers, or words.
Equation:
Student Response
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Advancing Student Thinking
Activity Synthesis
Invite previously identified students to share.
“How did the representation change when they added 3 ones? What stayed the same?” (You start with a full 10-frame and 4 ones, and when you add 3 more, that 10-frame does not change. This other 10-frame changed because now there are 4 red counters and 3 yellow counters.)
Activity 2
Standards Alignment
Building On
Addressing
1.OA.C.6
Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., ); decomposing a number leading to a ten (e.g., ); using the relationship between addition and subtraction (e.g., knowing that , one knows ); and creating equivalent but easier or known sums (e.g., adding by creating the known equivalent ).
The purpose of this activity is for students to add a one-digit number to a teen number. All of the totals are within 20. Students are provided 10-frames and two-color counters which they may choose to use to represent the sums. Using 10-frames 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 . It’s important that the teacher write the equation the way that students think about the answer to the problem. For example, the equation represents students who show 17 counters and count on as they add 2 more. The equation or represents students who see that the ten stays the same and they can add the ones to help them find the total.
MLR7 Compare and Connect. Synthesis: After the solutions have been presented, lead a discussion comparing, contrasting, and connecting the two equations. Ask, “How are these equations similar?” and “How are they different?” Advances: Representing, Conversing
Engagement: Develop Effort and Persistence. Chunk this task into more manageable parts. Check in with students to provide feedback and encouragement after each chunk. Supports accessibility for:Attention, Social-Emotional Functioning
Launch
Groups of 2
Give students access to double 10-frames and connecting cubes or two-color 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 in these ways:
Activity Synthesis
Display each equation with its unknown number.
Invite previously identified students to share.
“How does match _____’s work?” (They put 17 on and then counted 2 more—18, 19—to get the value.)
“How does match _____’s work?” (They added the ones and got 9 and then added 10 to get 19.)
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
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
Choose a center.
Compare
Number Puzzles
Find the Pair
Student Response
None
Advancing Student Thinking
Activity Synthesis
“How do you choose which center will be most helpful for you?”
Lesson Synthesis
Display and its double 10-frame 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 10-frames and see that both are filled, which is 20.)
Write equations to represent each student’s thinking.
Standards Alignment
Building On
Addressing
1.OA.D.7
Understand the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false. For example, which of the following equations are true and which are false? , , , .
Find the number that makes each equation true.
Show your thinking using drawings, numbers, or words.
Student Response
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Advancing Student Thinking
Building Toward
1.NBT.C.4
Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
