2.7 Adding and Subtracting within 1,000
Unit Goals
 Students use place value understanding, the relationship between addition and subtraction, and properties of operations to add and subtract within 1,000.
Section A Goals
 Add and subtract numbers within 1,000 without composition or decomposition, and use strategies based on the relationship between addition and subtraction and the properties of operations.
Section B Goals
 Add numbers within 1,000 using strategies based on place value understanding, including composing a ten or hundred.
Section C Goals
 Subtract numbers within 1,000 using strategies based on place value understanding, including decomposing a ten or hundred.
Section A: Add and Subtract within 1,000 without Composition or Decomposition
Problem 1
Preunit
Practicing Standards: 2.NBT.A.1, 2.NBT.A.3
Select all representations of the number 318.
Solution
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Problem 2
Preunit
Practicing Standards: 2.NBT.A.1, 2.NBT.A.3
Write a number for each representation.

Five hundred twentyseven
______________

\(300+60+8\)
______________

______________

\(5 + 40 + 700\)
______________
Solution
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Problem 3
Preunit
Practicing Standards: 2.NBT.B.5
Find the value of each sum or difference. Show your thinking.
 \(52  43\)
 \(65  19\)
 \(36 + 47\)
Solution
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Problem 4
Preunit
Practicing Standards: 1.NBT.C.5, 1.NBT.C.6
Find the value of each difference.
 \(77  10\)
 \(77  20\)
 \(90  70\)
Solution
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Problem 5
Find the value of each difference. Show your thinking.
 \(53  50\)
 \(285  281\)
 \(90  88\)
Solution
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Problem 6
 Here are Kiran's blocks.
He gives 2 tens to Priya.
What is the value of Kiran's blocks now? Show your thinking.

Then Priya gives Kiran 4 hundreds.
What is the value of Kiran's blocks now? Show your thinking.
Solution
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Problem 7
Find the value of each difference. Show your thinking. Use a number line or baseten blocks if it helps.
 \(648  25\)
 \(535  24\)
Solution
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Problem 8
 Find the value of \(600  289\). Show your thinking.
 Find the value of \(245 + 612\). Show your thinking.
Solution
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Problem 9
 \(365 + 214\)
 \(365  214\)
Solution
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Problem 10
Exploration
Here is Han's work finding the value of a difference.
 What difference did Han find? Show your reasoning.
 Write an addition and a subtraction equation that match Han's work.
Solution
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Problem 11
Exploration
Tyler says he can find the value of \(438  275\) using what he knows about differences of twodigit numbers.
“First I find \(43  27\) and then I find \(8  5\) and that gives me the answer.”
Use Tyler's reasoning to find the value of \(438  275\).
Solution
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Section B: Add within 1,000 using Place Value Strategies
Problem 1
Find the value of each sum. Show your thinking.
 \(238 + 52\)
 \(252 + 38\)
 \(119 +61\)
Solution
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Problem 2
Find the value of each sum. Explain your reasoning.
 \(395 + 77\)
 \(417 + 532\)
Solution
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Problem 3
Find the value of each sum. Show your thinking.
 \(238 + 54\)
 \(345 + 77\)
Solution
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Problem 4
Here is how Jada found the value of \(741 + 179\).
\(741 + 9 = 750\)
\(750 + 100 = 850\)
 Explain Jada's error.
 Correct Jada's work and find the value of \(741 + 179\).
Solution
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Problem 5
 Find the value of \(382 + 479\).

Find the missing digit that makes the equation true. Explain how you know.
\(534 + 4 \underline{\hspace{.5cm}} 6 = 1,\!000\)
Solution
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Problem 6
Exploration
Here is how Han likes to add.
 Explain why Han's method works.
 What do you think of Han's method?
 Use Han's method to find the value of \(388 + 259\).
Solution
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Problem 7
Exploration
Here is an equation with several digits missing.
\(\underline{\hspace{.5cm}} \ \underline{\hspace{.5cm}}5 + 63 \underline{\hspace{.5cm}} = 823\)
 What digits can you put in the blanks to make the equation true?
 Can you complete the numbers in more than one way to make the equation true?
Solution
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Section C: Subtract within 1,000 using Place Value Strategies
Problem 1

Find the value of each difference.
\(325  19\)
\(437  115\)

Jada drew this picture to find the value of a difference. What difference did Jada calculate? Explain how you know.
Solution
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Problem 2
Find the value of each difference. Show your thinking.

\(936  428\)

\(352  181\)
Solution
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Problem 3
Jada is finding the value of \(571  385\). She says that she can take the ones from the ones, tens from the tens, and hundreds from the hundreds, with no decomposing. Do you agree with Jada? Explain your reasoning.
Solution
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Problem 4
Find the value of each difference. Show your thinking.
 \(216  88\)
 \(803  564\)
Solution
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Problem 5
Find the value of each difference in a way that makes sense to you. Show your thinking.
 \(747  295\)
 \(811  255\)
 \(600  378\)
Solution
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Problem 6
Exploration
Here is how Kiran found the value of \(543  276\)
\(500  200 = 300\)
\(300  30 = 270\)
\(270  3 = 267\)
 Explain why Kiran's method works.
 Use Kiran's method to find \(325  276.\)
Solution
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Problem 7
Exploration
 Choose a threedigit number so that subtracting by place value is a good strategy for finding the value of \(637  \boxed{\phantom{8}} \boxed{\phantom{8}} \boxed{\phantom{8}}\). Explain your reasoning and find the value of the difference.
 Choose a threedigit number so that adding on to the smaller number is a good strategy for finding the value of \(637  \boxed{\phantom{8}} \boxed{\phantom{8}} \boxed{\phantom{8}}\). Explain your reasoning and find the value of the difference.
 Choose a threedigit number so that decomposing two different units is a good strategy for finding the value of \(637  \boxed{\phantom{8}} \boxed{\phantom{8}} \boxed{\phantom{8}}\). Explain your reasoning and find the value of the difference.
Solution
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