Objective
Use doubles facts to solve addition and subtraction problems within 20.
Student-Facing
I can use doubles facts as a strategy to solve addition and subtraction equations.
Common Core Standards
Core Standards
The core standards covered in this lesson
2.OA.B.2— Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.See standard 1.OA.6 for a list of mental strategies.
Operations and Algebraic Thinking
2.OA.B.2— Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers.See standard 1.OA.6 for a list of mental strategies.
Foundational Standards
The foundational standards covered in this lesson
1.OA.C.6
Operations and Algebraic Thinking
1.OA.C.6— Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
Criteria for Success
The essential concepts students need to demonstrate or understand to achieve the lesson objective
- Based on subtraction or addition equations determine if there is a related doubles fact.
- Use related fact to solve addition and subtraction equations.
- If it is a near doubles fact, adjust computation for plus 1 or 2 or minus one 1 or 2 instances.
Tips for Teachers
Suggestions for teachers to help them teach this lesson
- Known facts can be used when encouraging students to think flexibly about the patterns that they are noticing with numbers in equations. Be flexible with your students as they may vary in the way they notice relationships via doubles facts, sums within 10, and some students picking up on known facts as it relates to sums within 20.
- The end of year goal is to fluently add and subtract within 20 using mental strategies so students are still building up this skill at this point in the year.
- A reminder, fluency in math relates to flexible thinking, using appropriate strategies, efficiency, and accuracy, these things take time.
Lesson Materials
- Tens Frame Template (1 per student) — These can be laminated or in page protectors to reuse
- Two-sided counters (30 per student pair)
In Topic B, students can play "Choral Counting, Version 1" or "Behind My Back, Version 1". (Refer to the activity in the Fluency Activities Tool for further information about setup, procedure, and guiding questions,)
Suggestion for this lesson:
Choral Counting - Count 120 to 420 by tens
Behind My Back - Hide 5
Fishtank Plus
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Anchor Tasks
Tasks designed to teach criteria for success of the lesson, and guidance to help draw out student understanding
15-25 minutes
Problem 1
Nicholas wants to use a doubles fact to help him solve 8 + 9 = ? instead of the make a ten strategy. What doubles facts could he use?
Purpose
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Facilitation Guidance
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Problem 2
Solve. What doubles fact could help you solve these problems?
a.6 + 7 = _____
b.12 + 2 = _____
c.8 + 7= _____
d.13 + 4= _____
Purpose
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Facilitation Guidance
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Problem 3
Solve. Use drawings, numbers or words to show your thinking.
a._____ = 15 - 7
b._____ = 12 - 5
c.17 - 8 = _____
Purpose
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Facilitation Guidance
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Problem 4
What are two ways you could solve the following problems? Use drawings or numbers to show your thinking.
a.19 - 7 = ______
b.16 = 8 + _____
c.13 + _____ = 17
Purpose
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Facilitation Guidance
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Problem Set
15-20 minutes
Target Task
A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved
5-10 minutes
Find the missing number in each equation. For each one, name a doubles fact that helps you solve the problem.
a.5 + _____ = 11 Doubles Fact: ____________________
b.14 - 6 = _____ Doubles Fact: ____________________
c.7 + 8 = _____Doubles Fact: ____________________
d.16 - 9 = _____Doubles Fact: ____________________
e._____ + 9 = 17 Doubles Fact: ____________________
f.9 + 6 = _____ Doubles Fact: ____________________
Student Response
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Additional Practice
Daily Word Problems, Warm Ups, and Center Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.
Word Problems and Fluency Activities
Word Problems and Fluency Activities
Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.
Lesson 9
Lesson 11
