subtraction from addition - everyday math€¦ · practicing addition and subtraction facts my...
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Lesson 2�6 121
Advance Preparation
Teacher’s Reference Manual, Grades 1–3 pp. 197, 198
Key Concepts and Skills• Practice subtraction facts.
[Operations and Computation Goal 1]
• Use dominoes to model related addition
and subtraction facts.
[Operations and Computation Goal 1]
• Identify and use patterns to solve
subtraction facts.
[Patterns, Functions, and Algebra Goal 1]
• Use symbols to write number sentences
for fact families.
[Patterns, Functions, and Algebra Goal 2]
Key ActivitiesChildren make up and share number stories
that are solved by subtraction, discover and
practice the –0 and –1 shortcuts, and use
dominoes to generate related addition and
subtraction facts.
Ongoing Assessment: Recognizing Student Achievement Use an Exit Slip (Math Masters, page 415). [Patterns, Functions, and Algebra Goal 3]
Key Vocabularysubtraction number story � –0 facts �
–1 facts � –0 shortcut � –1 shortcut
MaterialsMath Journal 1, p. 35
Home Link 2�5
Math Masters, p. 415
1 domino per child � slate � 10 counters and
10 cubes (optional)
Practicing Addition and Subtraction FactsMy Reference Book, pp. 122, 123,
148 and 149
per partnership: 4 each of number
cards 0–10 (from the Everyday Math
Deck, if available)
Children review addition and
subtraction facts by playing Addition
Top-It and Subtraction Top-It.
Math Boxes 2�6Math Journal 1, p. 36
Children practice and maintain skills
through Math Box problems.
Home Link 2�6Math Masters, p. 31
Children practice and maintain skills
through Home Link activities.
READINESS
Exploring Domino FactsMath Masters, p. 32
dominoes
Children explore the relationship between
addition and subtraction facts using a
concrete model.
ENRICHMENTExploring Dice Subtraction with Negative DifferencesMath Masters, p. 33
dice � number line
Children use dice combinations to explore
differences and patterns in single-digit
subtraction.
Teaching the Lesson Ongoing Learning & Practice
132
4
Differentiation Options
������
Subtraction from Addition
Objectives To review the –0 and –1 shortcuts; and to guide
children to identify the subtraction facts related to given
addition facts.
c
eToolkitePresentations Interactive Teacher’s
Lesson Guide
Algorithms Practice
EM FactsWorkshop Game™
AssessmentManagement
Family Letters
CurriculumFocal Points
Common Core State Standards
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122 Unit 2 Addition and Subtraction Facts
Getting Started
Math Message Make up a story for the number model 10 - 3 = 7.
Home Link 2�5 Follow-Up Check that children were able to find the correct path from the child to the ice-cream cone.
Mental Math and ReflexesPose doubles-plus-1 and doubles-plus-2 facts. Suggestions:
NOTE Change-to-less (also called take-away
or taking-from) is the meaning of subtraction
most often encountered in schoolwork. The
comparison meaning of subtraction does not
involve take-away, because nothing is actually
taken away; the two sets of quantities are
just being compared. Children are not
expected to categorize subtraction stories as
“change-to-less” or “comparison” at this time.
6 + 6 = ? 12
8 + 8 = ? 16
7 + 7 = ? 14
6 + 7 = ? 13
8 + 9 = ? 17
7 + 8 = ? 15
6 + 8 = ? 14
8 + 10 = ? 18
7 + 9 = ? 16
1 Teaching the Lesson
� Math Message Follow-Up WHOLE-CLASS ACTIVITY
Write 10 - 3 = 7 on the board. Ask children to share their subtraction number stories. Draw an empty unit box. Have children suggest a label for each number story and write it in the unit box. Expect most of the children’s number stories to be one of two types:
Change-to-Less
Start with a number of items. Decrease the number of items. Find out the number of items after the number is decreased.For example: Tavon had 10 model cars. He lost 3 model cars. How many model cars does Tavon have now? 7 model cars
Children can model change-to-less number stories by representing the number in the story with counters. They remove the appropriate number of counters as described in the story. The number of counters remaining is the difference. They can also model the story on a number line by starting at the number showing the number of items and counting back the appropriate number of spaces as described in the story. The number they land on is the difference. (See margin.)
Comparison
Two separate quantities are known. Compare them by finding the difference between them. Tell how many more or less.For example: Supat has 10 model cars. Neal has 3 model cars. How many more model cars does Supat have? 7 more model cars
Children can model comparison number stories with sets of cubes, each representing the numbers being compared. They determine the answer by visually comparing the two sets of cubes. They can also model the story on a number line. (See margin.)
0 1 2 3 4 5 6 7 8 9 10
difference
0 1 2 3 4 5 6 7 8 9 10
difference
Change-to-Less
Comparison
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� Discussing the -0 and WHOLE-CLASS ACTIVITY
the -1 ShortcutsWrite some -0 facts and -1 facts on the board; do not include the differences. Use both horizontal and vertical forms.
Examples:
5 - 0 = 3 9 = 9 - 1 - 1 - 0 = 8 - 0
Ask children to copy and complete the facts on their slates. See whether they can describe the -0 shortcut and the -1 shortcut. If 0 is subtracted from any number, that number does not change. If 1 is subtracted from any number, the result is the next smaller number.
Write this problem on the board: 87 - 0 = . After a volunteer has given the answer, ask someone else to check the answer on a calculator. Try several other examples with 2- and 3-digit numbers, and with some large numbers, just for fun!
Follow the same procedure with several -1 examples. Use 2- and 3-digit numbers and a few large numbers.
� Using Dominoes to Generate WHOLE-CLASS ACTIVITY
Related Addition and Subtraction FactsDraw a domino on the board. Help children discover a set of related facts shown by the domino. For example, for a domino with 5 dots on one half and 4 dots on the other, ask:
● What is the total number of dots shown? 9
● Which addition facts describe this domino? 5 + 4 = 9 and 4 + 5 = 9
Remind children about turn-around facts.
Write the numbers 5, 4, and 9 on the board. Then write the two addition facts just named: 5 + 4 = 9 and 4 + 5 = 9.
● Which subtraction facts can you write using the three numbers 5, 4, and 9? 9 - 5 = 4 and 9 - 4 = 5 Write these two subtraction facts on the board.
Continue with other domino examples in the same way.
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Lesson 2�6 123
Adjusting the Activity
So children can recognize the
subtraction facts using dominoes, have them
erase or cover up one side of the domino.
For example: Nine dots in all. Take away the
5 dots on one side by erasing them. Four
dots remain. So, 9 - 5 = 4.
AUDITORY � KINESTHETIC � TACTILE � VISUAL
5+ 4
9
4+ 5
9
9- 5
4
9- 4
5
1. 2.
3. 4.
5. 6.
8. Write one addition fact and
7. one subtraction fact.
Domino FactsLESSON
2 �6
Date Time
For Problems 1 through 7, write 2 addition facts and 2 subtraction factsfor each domino.
+
+
-
-
+
+
-
-
+
+
-
-
+
-
+
+
-
-
+
+
-
-
+
+
-
-
+
6
42 +
6
24 -
4
62 -
2
64
Try This
10
64
10
46
6
104
4
106
14
86
14
68
8
146
6
148
11
38
11
83
3
118
8
113
18
99
9
189
14
95
14
59
9
145
5
149
9
90
9
09
9
90
0
99
12
57
12
75
5
127
7
125
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Math Journal 1, p. 35
Student Page
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124 Unit 2 Addition and Subtraction Facts
Math Boxes LESSON
2 �6
Date Time
1. Fill in the missing numbers.
3. Write the sums.
10 + 5 = 10 + 6 = 10 + 7 = 10 + 8 =
6. What time is it?
: What time
will it be in 15 minutes?
:
4. Write these numbers in order from smallest to largest. Begin with the smallest number.
133, 146, 129, 151 , , ,
5. Put an X on the digit in the tens place.
456
309
144
155
Unit
12 12
3
4567
8
9
1011
°F
50
60
96
10 80 81
2. What is the temperature? Fill in the circle next to the best answer.
A 55 degrees
B 62 degrees
C 52 degrees
D 56 degrees
15
15
30
7
7
154164 165
129 133 146 151
166156
161718
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Math Journal 1, p. 36
Student Page
Name Date Time
Today we learned that addition problems and subtraction problems are related. For example, 5 + 3 = 8 can be rewritten to show two related subtraction facts: 8 - 5 = 3 and 8 - 3 = 5.
Each domino shown below can be used to write 2 addition facts and 2 relatedsubtraction facts.
Please return this Home Link to school tomorrow.
Family Note
HOME LINK
2�6 Domino Facts
+
14
59 +
14
95 -
5
149 -
9
145
+
15
96 +
15
69 -
9
156 -
6
159
+
15
87 +
15
78 -
8
157 -
7
158
Write 2 addition facts and 2 subtraction facts for each domino.
1. 2.
7
+ 3
10
3
+ 7
10
10
- 3
7
10
- 7
3
3. 4.
Write the sums. Tell someone at home what you knowabout doubles-plus-1 and doubles-plus-2 facts.
5. 6 + 7 = 13 6. 14 = 8 + 6
7. 5 + 7 = 12 8. 7 + 9 = 16
Unit
25
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Math Masters, p. 31
Home Link Master
� Practicing Domino Facts INDEPENDENTACTIVITY
(Math Journal 1, p. 35)
Children write the addition and subtraction facts generated by each domino pattern on the journal page. The final problems include special features that may cause some children difficulty. The double-9 domino has only two related facts, not four: 9 + 9 = 18 and 18 - 9 = 9. The domino with 9 dots on the top and zero dots on the bottom may confuse children. Make sure children realize that the blank half of the domino stands for zero. The four related facts for this domino are 9 + 0 = 9, 0 + 9 = 9, 9 - 0 = 9, and 9 - 9 = 0.
Ongoing Assessment: Exit Slip
Recognizing Student Achievement
Use an Exit Slip (Math Masters, page 415) to assess children’s understanding of
the turn-around facts. Give each child a domino. Have them write two addition
and two subtraction facts for that domino. Children are making adequate
progress if they can write the corresponding addition problem and the
turn-around fact. Some children may be able to successfully write two
corresponding subtraction problems.
[Patterns, Functions, and Algebra Goal 3]
2 Ongoing Learning & Practice
� Practicing Addition and Subtraction Facts
PARTNER ACTIVITY
(My Reference Book, pp. 122, 123, 148, and 149)
Children practice addition and subtraction facts by playing Addition Top-It and Subtraction Top-It. Provide time for children to play both games. Children were introduced to Addition Top-It in Lesson 1-4. For instructions, see My Reference Book, pages 122 and 123. Subtraction Top-It is played similarly. See My Reference Book, pages 148 and 149. Read the rules with the class and model a round or two prior to having children play in partnerships or small groups.
� Math Boxes 2�6 INDEPENDENTACTIVITY
(Math Journal 1, p. 36)
Mixed Practice Math Boxes in this lesson are paired with Math Boxes in Lesson 2-8. The skills in Problems 5 and 6 preview Unit 3 content.
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Math Masters, p. 32
Teaching Master
Lesson 2�6 125
� Home Link 2�6 INDEPENDENTACTIVITY
(Math Masters, p. 31)
Home Connection Children use dominoes to generate and solve related addition and subtraction facts. Children also practice doubles-plus-1 and doubles-plus-2 facts.
3 Differentiation Options
READINESS INDEPENDENTACTIVITY
� Exploring Domino Facts 5–15 Min
(Math Masters, p. 32)
To explore the relationship between addition and subtraction facts using a concrete model, have children use dominoes to model facts. Children complete Math Masters, page 32. When they have finished the page, discuss when they added and when they subtracted to find the missing numbers. (Note that some children may add up instead of subtracting when solving the domino problems.)
ENRICHMENT INDEPENDENTACTIVITY
� Exploring Dice Subtraction 5–15 Min
with Negative Differences(Math Masters, p. 33)
To apply children’s understanding of subtraction, have them solve randomly generated single-digit subtraction problems. They record their work on Math Masters, page 33. Discuss the patterns they see on the page. When the two numbers are switched in the problem, the differences are the same distance from zero on the number line. When you subtract the larger number from the smaller number, the difference is a negative number.
Planning Ahead
If children have not cut out the Fact Triangles from Activity Sheets 1 and 2, have them do that soon. They will be used in Lesson 2-7.
For each problem below:
1. Roll two dice.
2. Record the numbers you rolled.
3. Write two subtraction number models for the numbersyou rolled.
4. Use a number line to solve your problems. (Hint: Sometimes your answers will be negative numbers.)
Example:
I rolled 4 and 5.
5 – 4 = 1 and 4 – 5 = -1.
1. I rolled and .
- = - =
2. I rolled and .
- = - =
3. I rolled and .
- = - =
LESSON
2�6
Name Date Time
Dice Subtraction
Try This
Each time you roll the dice, how could you use one of your subtraction problems to help you solve the other?Sample answer: Each answer will be the samedistance from 0 on the number line.
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Math Masters, p. 33
Teaching Master
gg
Fill in the missing dots and missing numbers for each problem below. Hint: You can look at dominoes to help you figure out what the dots look like.
1. 7 2. 11 3. 12
4 3 5 6 7 5
4. 5. 6.
4 6 9
Make up one of your own.
7.
151210
666
Sample answer: When I know the total
I can subtract to find the other number of dots.number of dots and the number of dots on half of the domino,
Name Date Time
LESSON
2�6 Domino Facts
Explain when you think subtraction facts might help you solvethe problems above.
Try This
Answers vary.
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