options: Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.

Explain why addition and subtraction strategies work, using place value and the properties of operations. (Explanations may be supported by drawings or objects.)

Add and subtract within 1000, 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. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

Add up to four two-digit numbers using strategies based on place value and properties of operations.

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
problem_activity: Narrative
In this activity, students find the value of sums with larger numbers using any method that makes sense to them. They may represent their thinking using connecting cubes, drawings, equations, or words. Monitor for the ways students use methods based on place value, including the language they use to describe composing a ten when adding tens and tens and ones and ones (MP3, MP6).
MLR8 Discussion Supports.
Synthesis: After a strategy is presented to the class, invite students to turn to a partner and restate what they heard in their own words. Encourage students to borrow language from a display with words and phrases collected from previous lessons.
Advances: Listening, Speaking
Required Materials
Materials to Gather
Connecting cubes
Required Preparation
Create connecting cubes in towers of 10 and singles.
Launch
Groups of 2
Give students access to connecting cubes in towers of 10 and singles.
“Now we are going to add larger numbers. Think about how you can show your thinking so others can understand.”
“You have time to work independently before sharing your thinking with a partner.”
Activity
5 minutes: independent work time
5 minutes: partner discussion
Monitor for students who:
Add by place value (
\(27 + 15\)
,
\(20 + 10 = 30\)
,
\(7 + 5 = 12\)
,
\(30 + 12 = 42\)
)
Decompose 1 number to make a 10, then add the rest (
\(27 + 15\)
,
\(27 + 3 = 30\)
,
\(30 + 12 = 42\)
)
Student Facing
Find the value of each sum. Show your thinking using drawings, numbers, or words.
\(37 + 8\)
\(24 + 23\)
\(16 + 30\)
\(39 + 11\)
\(27 + 15\)
Student Response
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Activity Synthesis
Display
\(27 + 15\)
.
Select previously identified students to share.


correct_option_index: 4