Lesson 2
Add and Subtract with Tens and Hundreds
Warmup: Number Talk: Add Multiples of 10 (10 minutes)
Narrative
Launch
 Display one expression.
 “Give me a signal when you have an answer and can explain how you got it.”
 1 minute: quiet think time
Activity
 Record answers and strategy on an open number line.
 Keep expressions and work displayed.
 Repeat with each expression.
Student Facing
Find the value of each expression mentally.
 \(34 + 20\)
 \(34 + 60\)
 \(58 + 30\)
 \(158 + 40\)
Student Response
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Activity Synthesis
 “How did you find the value of these expressions?” (We noticed we could count on by tens. We added the number of tens in each one. The number in the ones place didn’t change.)
Activity 1: Show It with Baseten Blocks (15 minutes)
Narrative
The purpose of this activity is to add and subtract threedigit numbers and multiples of 10 or 100 using baseten blocks and equations. The structure of the baseten blocks encourages students to notice that hundreds are added to or subtracted from hundreds and tens are added to or subtracted from tens (MP7). To help students focus on this structure, the numbers are chosen so that the addition and subtraction of tens can take place without needing to compose or decompose a hundred.
If you do not have enough hundred blocks for each group of 2 students, students may work in larger groups.
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give each group baseten blocks and a number cube.
Activity
 “Work with your partner to show each number with baseten blocks.”
 “Take turns rolling the number cube to see how many tens or hundreds to add or subtract.”
 10 minutes: partner work time
 Monitor for students to share their equations for the number of hundreds they subtract from 805.
Student Facing
Use your baseten blocks to show each number. Then, roll a number cube to see how many tens or hundreds to add or subtract.

Show 297.
 Add _____ hundreds.
 Complete the equation: \(297 + \underline{\hspace{1cm}} =\underline{\hspace{1cm}}\)

Show 432.
 Add _____ tens.
 \(432 + \underline{\hspace{1cm}} =\underline{\hspace{1cm}}\)

Show 982.
 Subtract _____ tens.
 \(982  \underline{\hspace{1cm}} =\underline{\hspace{1cm}}\)

Show 351.
 Add _____ hundreds.
 Write an equation:

Show 805.
 Subtract ____ hundreds.
 Write an equation:
Student Response
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Activity Synthesis
 Invite previously identified students to share equations or display
 \(805  400 = 405\)
 Display a baseten diagram, or, if possible, allow students to demonstrate with baseten blocks.
 “How does the equation connect to the diagram or blocks?” (You take away 4 hundreds from the blocks and you’re left with 4 hundreds and 5 ones.)
 “What did you notice about how the value of the blocks changed?” (There are fewer blocks. The hundreds place changed because you subtracted hundreds.)
Activity 2: How Many with Baseten Blocks and Equations (20 minutes)
Narrative
The purpose of this activity is for students to add and subtract multiples of 10 and 100 within 1,000. Students interpret situations with baseten blocks and baseten diagrams and use equations to represents sums and differences. In the activity synthesis, students relate the situation, baseten diagram, and equation and notice, through repeated reasoning, that when adding and subtracting, one can add or subtract hundreds and hundreds and tens and tens (MP7, MP8).
Advances: Representing, Conversing
Supports accessibility for: Conceptual Processing, Language, Organization
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give students access to baseten blocks.
Activity
 “These students were using baseten blocks to find the value of sums and differences.”
 “For each problem, represent the student’s value in a way that makes sense to you. You can use baseten blocks, diagrams, or equations.”
 10 minutes: partner work time
 For Priya and Jada’s blocks, monitor for students who:
 write equations to show the sums and differences.
 use baseten diagrams to show subtraction.
Student Facing

Mai has 2 hundreds, 2 tens, and 3 ones. Lin has 4 hundreds.
Represent their values with baseten blocks or diagrams.
What is the value of their blocks altogether? Show your thinking.

Andre has 4 hundreds, 2 tens, and 8 ones.
Represent his value with baseten blocks or diagrams.
Andre gives 2 hundreds to Clare.
What is the value of his blocks now? Show your thinking.

Diego has 6 tens. Tyler has 8 hundreds, 3 tens, and 6 ones.
What is the value of their blocks together? Show your thinking.

Elena has 5 hundreds, 7 tens, and 2 ones. She gives 2 tens to Kiran.
What is the value of her blocks now? Show your thinking.

Priya has 6 hundreds, 5 tens, and 8 ones. Han gives her 3 hundreds.
What is the value of her blocks now? Show your thinking.

Jada has 4 hundreds, 8 tens, and 2 ones. She gives 3 hundreds to Noah.
What is the value of her blocks now? Show your thinking.
Student Response
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Advancing Student Thinking
If students draw diagrams that do not match the situation or write equations that are not true, consider asking:
 “Can you explain what you did?”
 “Do you notice any patterns when you add or subtract hundreds and hundreds? Tens and tens?”
Activity Synthesis
 Invite a student to share their representation and equation for Jada’s blocks. If no students use a baseten diagram, select a student to share how they use baseten blocks, and use a baseten diagram to record their steps.
 “How does the baseten diagram show Jada’s blocks?” (The blocks show how many Jada started with. The lines show the 3 hundreds that were taken away.)
 Display \(482  300 = 182\)
 “How does the equation show Jada’s blocks?” (482 is what Jada started with and 300 is the 3 hundreds she gave away. 182 is how much she has left.)
Lesson Synthesis
Lesson Synthesis
“Today you added and subtracted hundreds or tens to and from threedigit numbers.”
Invite previously identified students to share representations for Priya’s blocks.
Display \(658 + 300 = 958\).
“How is the representation of Jada’s blocks different from the representation for Priya’s blocks?” (Jada’s blocks show 3 hundreds crossed out. Priya’s show 3 hundreds added.)
Cooldown: How Many Blocks? (5 minutes)
CoolDown
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