Grade 2 · Operations · MAT-02-OPS-001
Addition Facts Within 20 Fluency
Recall or efficiently derive addition facts within 20.
Learning objectives
What you should be able to do
- Recall or efficiently derive addition facts within 20.
- Use strategies such as making ten, doubles, and near-doubles.
- Explain why a chosen strategy works.
Prerequisite check
Make sure the foundation is ready.
Checks readiness to move from strategy use toward fluency.
Learn
Build the idea from meaning, not memorization.
Fluency means accurate, efficient, and flexible
Fluency is not only speed. A fluent learner can produce correct sums, choose a useful strategy, and explain the relationship between facts.
Making ten reduces cognitive load
For 8+7, take 2 from 7 to make 8+2=10, leaving 5. Then 10+5=15. The total is unchanged because the addends were decomposed and recombined.
Doubles and near-doubles are anchors
Known doubles such as 6+6=12 support nearby facts. Since 6+7 is one more than 6+6, the sum is 13.
Commutativity connects fact pairs
If 4+9=13, then 9+4=13. Recognizing this reduces the number of unrelated facts a learner must store.
Interactive math lab
Change it. See what stays true.
Ten-Frame Lab
Fill the frame from left to right and connect the visible amount to the numeral.
5 filled; 5 empty; 10 spaces altogether.
- make ten
- double
- near double
- commutative pair
Worked examples
Twenty different ways to see the concept work.
8+7
15Make 10: 8+2+5.
9+6
15Make 10: 9+1+5.
6+6
12Double 6.
6+7
13Near-double: 6+6+1.
7+8
15Near-double or make ten.
5+9
149+1+4.
4+8
128+2+2.
3+9
129+1+2.
7+7
14Double 7.
8+8
16Double 8.
9+9
18Double 9.
2+9
119+1+1.
4+7
117+3+1.
5+6
11Double 5 plus 1.
3+8
118+2+1.
6+9
159+1+5.
2+8
10Make exactly 10.
7+3
10Make exactly 10.
4+9 vs 9+4
both 13Commutative property.
8+5
138+2+3.
Practice
Guided practice with hints
018+6
Hint: Make 10 from 8.
Answer: 14
027+7
Hint: Use a double.
Answer: 14
035+6
Hint: Use double 5 plus 1.
Answer: 11
049+4
Hint: Make 10.
Answer: 13
056+8
Hint: Use 7+7 or make 10.
Answer: 14
063+9
Hint: Move 1 to 9.
Answer: 12
Practice
Independent practice
018+7
Answer: 15
029+5
Answer: 14
036+6
Answer: 12
047+8
Answer: 15
054+9
Answer: 13
065+7
Answer: 12
073+8
Answer: 11
089+9
Answer: 18
Common mistakes
Learn to catch the error, not just the answer.
Use known anchors such as 10s and doubles for efficiency.
Move part of one addend without adding or removing quantity overall.
Use commutativity: a+b=b+a.
Applications & challenge
Use the idea beyond a single exercise.
Applications
- Mentally combine small counts in games, shopping, or scorekeeping.
- Use quick sums to check larger written addition.
Challenge problems
Explain two strategies for 8+7.
For example make 10 and near-double.
Which is easier to derive from 7+7: 7+8 or 9+4?
7+8
Why does moving 2 from 7 to 8 preserve 8+7?
The total quantity of the two addends remains 15.
Find three pairs that make 10.
Examples: 1+9,2+8,3+7.
Flashcards
Retrieve it from memory.
Flashcards
Card 1 of 6
Game mode
Fact Strategy Sprint
Solve facts within 20 by selecting a strategy and answer.
Practice
Mastery check
018+6
Answer: 14
029+7
Answer: 16
036+6
Answer: 12
047+8
Answer: 15
055+9
Answer: 14
063+8
Answer: 11
07Name one efficient strategy.
Answer: Make ten, doubles, near-doubles, or commutativity.
08Explain fluency.
Answer: Accurate, efficient, flexible fact solving.
Terminology
Words to know
- fluency
- Accurate, efficient, and flexible use of mathematical facts.
- double
- A sum with two equal addends.
- near-double
- A fact close to a known double.
- commutative property
- Changing addend order does not change the sum.
Continue learning
Connected concepts
Curriculum references
Standards and instructional references
California Common Core State Standards for Mathematics — 2.OA.B.2
Fluency with addition within 20.