G2 U6 L2-P.pub
Subtract 2-Digit Numbers: Draw a Picture Strategy
Applied MP
MPs * Embedded MP
Procedural Lesson Grade 2 · Unit 6 · Lesson 2
1
*
MC: 2.NBT.5▲
2
3
4
*
*
5
6
7
8
*
*
Student Journal Pages
63-70
Problem of the Day
Objective: Today, I will use the draw a picture strategy to subtract two-digit
numbers with and without bundling/regrouping.
Vocabulary
Teacher Resources Considerations:
Draw a picture strategy: 52 — 28 = Tens
Ones
| | | | |
2
4
Working form: 4 12
5 2 —2 8 2 4
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 moves from the use of manipulatives to representational drawings of differences within 100 with regrouping, and relates drawings to a written method (working form). Continue to support students with base ten blocks, if needed. 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. Clearly explain the connection between the strategy and the working form. Remind students to quickly draw base ten blocks by using a square for a hundred square, a line for a ten rod, and a dot for a one cube. So, 123 is represented: | | ●●● In Unit 4, students were given a table in which to complete addition with regrouping in working form. Here the scaffold has been removed. Students who need place values marked should draw a table in the working form area.
Materials:
Use the materials prepared for Lesson 1, if needed.
Steps: 1. 2.
3. 4. 5.
Draw the minuend in the place value chart. Subtract the subtrahend from the cubes in the ones place. If necessary, cross out a ten rod in the tens place and draw 10 unit cubes in the ones place. Subtract the subtrahend from the rods in the tens place. Record the difference. Write the problem in working form.
Application of MPs: MP7: MP8:
Copyright © Swun Math
What concept or rule helps you solve the problem? The concept or rule that helps me solve the problem is . How do you know your answer seems reasonable? I know my answer is reasonable because . Grade 2 Unit 6 Lesson 2 P TE
Answer Key
Answer Key: I/M
SGP
FCU
SP
CH
HW
1. 21; no.
1. 46; yes.
1. 7; yes
1. 15; yes.
1. She forgot to take away the
1. 20; no.
ten she regrouped. The answer should be 78.
2. 18; yes.
2. 12; no.
2. 23; yes.
2. 65; yes.
2. He represented 74 and
2. 29; yes.
subtracted 23 which did not represent the correct problem. The answer should be 49.
3. 21; no.
3. 39; yes.
EXT: Possible answer: You can build 76 (the difference) plus 19 (the subtrahend). 6
4. 44; yes.
+ 9 regroups a ten, leaving
4. 46; no.
5 in the ones place. 70 + 10 + 10 = 90. 90 + 5 = 95. Since the sum is the same as the 5. He drew 24 instead of 22 base ten blocks and subtracted 12 instead of 14. The answer should be 8.
minuend (starting number), the answer is correct.
5. 14; yes.
76 + 19 95
6. 57; yes
6. 44; yes.
*NOTE: For all questions, check student pictures.
Sample Response to MP questions:
MP7: What concept or rule helps you solve these problems? The rule/concept that helps me solve the problem is composing and decomposing numbers. MP8: How do you know your answer seems reasonable? I know my answer is reasonable because I can check my work using addition.
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Input / Model (Teacher Presents)
*MP1: Make sense of the problem and persevere in solving it! *MP8: Find a strategy to help solve the problem. Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 72 – 51 = Tens
| | | |
Ones
Working Form:
7 2 —5 1 2 1
| | | 2
1
72 — 51 = 21 Did you need to unbundle/regroup a ten?
NO
2. 33 – 15 = Tens
| | |
1
Ones
Working Form:
2 13
3 3 —1 5 18
8
33 — 15 = 18 Did you need to unbundle/regroup a ten?
YES
MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer seems reasonable? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Structured Guided Practice (A / B Partners Practice) Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 65 – 19 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
2. 28 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer seems reasonable? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Final Check for Understanding (White Board Time or Circulate & Check Work) Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 35 – 28 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
2. 71 – 48 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Student Practice
Name: ____________________________
Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
Date: ______________________________ Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 62 – 47 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 2. 81 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 3. 37 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Student Practice Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
4. 93 – 49 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 5. Jamie solved the following subtraction problem. What did he do wrong? 22 – 14 = Tens
Ones
| |
Find the correct difference. 6. 80 – 23 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Challenge Problems Directions: Read and answer each question.
1. Jenny solved the following subtraction problem. What did she do wrong? 83 – 5 =
2. George solved the following subtraction problem. What did he do wrong? 73 – 24 =
T
O
T
O
| | | |
| | | |
8
4
| | | | 8
Find the correct difference.
| | |
11
Find the correct difference.
Extension
*MP4: Apply mathematics in everyday life.
Explain how you could use base ten blocks to check to see if you solved 95 – 19 = 76 correctly.
Reaching Consensus
*MP3: Do you agree/disagree with what
said?
Student Presentations
*MP6: How do you know your answers are correct/reasonable?
Closure Recap today’s lesson with one or more of the following questions:
MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer is reasonable?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Homework
Name: ____________________________
Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
Date: ______________________________ Directions: Solve using the draw a picture strategy. Write the problem in working form.
Example: 31 — 12 =
Tens
Ones
| | |
1
9
Working Form: 2 11
3 1 —1 2 19
31 — 12 = 19 1. 28 – 8 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 2. 58 – 29 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 3. 66 – 27 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Homework Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
4. 69 – 23 = Tens
Working Form: Ones
Did you need to unbundle/regroup a ten? 5. 51 – 37 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 6. 72 – 28 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Applied MP
MPs * Embedded MP
Procedural Lesson Grade 2 · Unit 6 · Lesson 2
1
*
MC: 2.NBT.5▲
2
3
4
*
*
5
6
7
8
*
*
Student Journal Pages
63-70
Problem of the Day
Objective: Today, I will use the draw a picture strategy to subtract two-digit
numbers with and without bundling/regrouping.
Vocabulary
Teacher Resources Considerations:
Draw a picture strategy: 52 — 28 = Tens
Ones
| | | | |
2
4
Working form: 4 12
5 2 —2 8 2 4
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 moves from the use of manipulatives to representational drawings of differences within 100 with regrouping, and relates drawings to a written method (working form). Continue to support students with base ten blocks, if needed. 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. Clearly explain the connection between the strategy and the working form. Remind students to quickly draw base ten blocks by using a square for a hundred square, a line for a ten rod, and a dot for a one cube. So, 123 is represented: | | ●●● In Unit 4, students were given a table in which to complete addition with regrouping in working form. Here the scaffold has been removed. Students who need place values marked should draw a table in the working form area.
Materials:
Use the materials prepared for Lesson 1, if needed.
Steps: 1. 2.
3. 4. 5.
Draw the minuend in the place value chart. Subtract the subtrahend from the cubes in the ones place. If necessary, cross out a ten rod in the tens place and draw 10 unit cubes in the ones place. Subtract the subtrahend from the rods in the tens place. Record the difference. Write the problem in working form.
Application of MPs: MP7: MP8:
Copyright © Swun Math
What concept or rule helps you solve the problem? The concept or rule that helps me solve the problem is . How do you know your answer seems reasonable? I know my answer is reasonable because . Grade 2 Unit 6 Lesson 2 P TE
Answer Key
Answer Key: I/M
SGP
FCU
SP
CH
HW
1. 21; no.
1. 46; yes.
1. 7; yes
1. 15; yes.
1. She forgot to take away the
1. 20; no.
ten she regrouped. The answer should be 78.
2. 18; yes.
2. 12; no.
2. 23; yes.
2. 65; yes.
2. He represented 74 and
2. 29; yes.
subtracted 23 which did not represent the correct problem. The answer should be 49.
3. 21; no.
3. 39; yes.
EXT: Possible answer: You can build 76 (the difference) plus 19 (the subtrahend). 6
4. 44; yes.
+ 9 regroups a ten, leaving
4. 46; no.
5 in the ones place. 70 + 10 + 10 = 90. 90 + 5 = 95. Since the sum is the same as the 5. He drew 24 instead of 22 base ten blocks and subtracted 12 instead of 14. The answer should be 8.
minuend (starting number), the answer is correct.
5. 14; yes.
76 + 19 95
6. 57; yes
6. 44; yes.
*NOTE: For all questions, check student pictures.
Sample Response to MP questions:
MP7: What concept or rule helps you solve these problems? The rule/concept that helps me solve the problem is composing and decomposing numbers. MP8: How do you know your answer seems reasonable? I know my answer is reasonable because I can check my work using addition.
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Input / Model (Teacher Presents)
*MP1: Make sense of the problem and persevere in solving it! *MP8: Find a strategy to help solve the problem. Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 72 – 51 = Tens
| | | |
Ones
Working Form:
7 2 —5 1 2 1
| | | 2
1
72 — 51 = 21 Did you need to unbundle/regroup a ten?
NO
2. 33 – 15 = Tens
| | |
1
Ones
Working Form:
2 13
3 3 —1 5 18
8
33 — 15 = 18 Did you need to unbundle/regroup a ten?
YES
MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer seems reasonable? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Structured Guided Practice (A / B Partners Practice) Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 65 – 19 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
2. 28 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer seems reasonable? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Final Check for Understanding (White Board Time or Circulate & Check Work) Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 35 – 28 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
2. 71 – 48 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Student Practice
Name: ____________________________
Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
Date: ______________________________ Directions: Solve using the draw a picture strategy. Write the problem in working form.
1. 62 – 47 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 2. 81 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 3. 37 – 16 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Student Practice Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
4. 93 – 49 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 5. Jamie solved the following subtraction problem. What did he do wrong? 22 – 14 = Tens
Ones
| |
Find the correct difference. 6. 80 – 23 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Challenge Problems Directions: Read and answer each question.
1. Jenny solved the following subtraction problem. What did she do wrong? 83 – 5 =
2. George solved the following subtraction problem. What did he do wrong? 73 – 24 =
T
O
T
O
| | | |
| | | |
8
4
| | | | 8
Find the correct difference.
| | |
11
Find the correct difference.
Extension
*MP4: Apply mathematics in everyday life.
Explain how you could use base ten blocks to check to see if you solved 95 – 19 = 76 correctly.
Reaching Consensus
*MP3: Do you agree/disagree with what
said?
Student Presentations
*MP6: How do you know your answers are correct/reasonable?
Closure Recap today’s lesson with one or more of the following questions:
MP7: What concept or rule helps you solve these problems? MP8: How do you know your answer is reasonable?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Homework
Name: ____________________________
Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
Date: ______________________________ Directions: Solve using the draw a picture strategy. Write the problem in working form.
Example: 31 — 12 =
Tens
Ones
| | |
1
9
Working Form: 2 11
3 1 —1 2 19
31 — 12 = 19 1. 28 – 8 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 2. 58 – 29 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 3. 66 – 27 =
Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
Homework Unit 6 Lesson 2: Subtract 2-Digit Numbers: Draw a Picture Strategy
4. 69 – 23 = Tens
Working Form: Ones
Did you need to unbundle/regroup a ten? 5. 51 – 37 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten? 6. 72 – 28 = Tens
Ones
Working Form:
Did you need to unbundle/regroup a ten?
Copyright © Swun Math
Grade 2 Unit 6 Lesson 2 P TE
