G2 U6 L1-C.pub
Subtract 2-Digit Numbers: Build & Subtract on a Place Value Chart
Applied MP
MPs * Embedded MP
Conceptual Lesson Grade 2 · Unit 6 · Lesson 1
1
*
MC: 2.NBT.5▲
2
3
4
5
6
7
*
Student Journal Pages
57-62
Problem of the Day
Objective: Today, I will use base ten blocks to decide if I need to regroup/
bundle when subtracting two-digit numbers.
Vocabulary
Teacher Resources
Build and subtract numbers on a place value chart: 52 — 28 = Tens
2
Ones
4
Considerations: A goal of this unit is to help students learn to subtract by moving from the use of concrete manipulatives (base ten blocks) to representational drawings, then to numerical representations, and finally to a written method (algorithm). This lesson makes use of manipulatives to build the concept of regrouping. Remind students when adding, sometimes it is necessary to bundle (compose) sets of 10 base ten blocks and regroup them to the next higher place value. The reverse is true of subtraction. Sometimes it is necessary to break apart or unbundle (decompose) a base ten block and regroup the set of 10 to the next lower place value to have enough to subtract. This is why subtraction should begin from the ones place. Use the terms break apart, unbundle, decompose, and regroup so students become familiar with a variety of ways to describe subtraction.
Materials:
Place Value Chart (page 2, also provided in the Student Journal) Base ten blocks (ones, tens, hundred) (page 3, reproduce for classroom use)
Steps: 1. 2.
3. 4.
Build the minuend in the place value chart. Subtract the subtrahend from the cubes in the ones place. If necessary, unbundle a ten rod from the tens place and move the 10 unit cubes to the ones place. Subtract the subtrahend from the rods in the tens place. Record the difference.
Application of MPs: MP7:
MP8:
Copyright © Swun Math
8
What concept or rule helps you solve these problems? The rule/concept that helps me solve the problem is . How do you know your answer is reasonable? I know my answer is reasonable because .
Grade 2 Unit 6 Lesson 1 C TE
Answer Key
Answer Key: I/M
SGP
FCU
HW
1. See IM #1
1. See SGP #1
1. 48
1. >
21 — 9 = 12
32 — 8 = 24
2. See IM #2
2. See SGP #2
36 — 17 = 19
43 — 24 = 19
54 — 6 = 48
2. 6
2. >
64 — 58 = 6
3. =
4.
Applied MP
MPs * Embedded MP
Conceptual Lesson Grade 2 · Unit 6 · Lesson 1
1
*
MC: 2.NBT.5▲
2
3
4
5
6
7
*
Student Journal Pages
57-62
Problem of the Day
Objective: Today, I will use base ten blocks to decide if I need to regroup/
bundle when subtracting two-digit numbers.
Vocabulary
Teacher Resources
Build and subtract numbers on a place value chart: 52 — 28 = Tens
2
Ones
4
Considerations: A goal of this unit is to help students learn to subtract by moving from the use of concrete manipulatives (base ten blocks) to representational drawings, then to numerical representations, and finally to a written method (algorithm). This lesson makes use of manipulatives to build the concept of regrouping. Remind students when adding, sometimes it is necessary to bundle (compose) sets of 10 base ten blocks and regroup them to the next higher place value. The reverse is true of subtraction. Sometimes it is necessary to break apart or unbundle (decompose) a base ten block and regroup the set of 10 to the next lower place value to have enough to subtract. This is why subtraction should begin from the ones place. Use the terms break apart, unbundle, decompose, and regroup so students become familiar with a variety of ways to describe subtraction.
Materials:
Place Value Chart (page 2, also provided in the Student Journal) Base ten blocks (ones, tens, hundred) (page 3, reproduce for classroom use)
Steps: 1. 2.
3. 4.
Build the minuend in the place value chart. Subtract the subtrahend from the cubes in the ones place. If necessary, unbundle a ten rod from the tens place and move the 10 unit cubes to the ones place. Subtract the subtrahend from the rods in the tens place. Record the difference.
Application of MPs: MP7:
MP8:
Copyright © Swun Math
8
What concept or rule helps you solve these problems? The rule/concept that helps me solve the problem is . How do you know your answer is reasonable? I know my answer is reasonable because .
Grade 2 Unit 6 Lesson 1 C TE
Answer Key
Answer Key: I/M
SGP
FCU
HW
1. See IM #1
1. See SGP #1
1. 48
1. >
21 — 9 = 12
32 — 8 = 24
2. See IM #2
2. See SGP #2
36 — 17 = 19
43 — 24 = 19
54 — 6 = 48
2. 6
2. >
64 — 58 = 6
3. =
4.
