🎓 Grade 1📄 Free PDF✅ Answer Keys🎯 4 Classroom Sets

Subtraction Facts within 20 · Free Worksheets (Grade 1)

Practice subtraction facts within 20 (Grade 1) with free printable PDF worksheets. 4 pre-packaged classroom sets with 100% verified step-by-step answer keys, plus an unlimited live customizer for teachers and homeschoolers.

📐Aligned to Common Core (CCSS.MATH.CONTENT.1.OA.C.6)·5-10 min per sheet

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PanMaths.comSubtraction Facts within 20 Worksheets • Set A (Standard)

Name: __________________________

Date: _____________ Period: ____

Score: _____ / 10

12−1

Workspace:

13−12

Workspace:

11−5

Workspace:

13−1

Workspace:

17−15

Workspace:

4−3

Workspace:

11−6

Workspace:

19−6

Workspace:

9−2

Workspace:

10.

20−13

Workspace:

PanMaths.com • Free Printable Math WorksheetsPage 1 of 2

PanMaths.comAnswer Key & Worked Solutions • Set A (Standard)

Answer Key

Total Problems: 10

12−1= 11

1. Core Subtraction Fact: 12 − 1 = 11

2. Inverse Addition Proof: 11 + 1 = 12 ✅

13−12= 1

1. Core Subtraction Fact: 13 − 12 = 1

2. Inverse Addition Proof: 1 + 12 = 13 ✅

11−5= 6

1. Core Subtraction Fact: 11 − 5 = 6

2. Inverse Addition Proof: 6 + 5 = 11 ✅

13−1= 12

1. Core Subtraction Fact: 13 − 1 = 12

2. Inverse Addition Proof: 12 + 1 = 13 ✅

17−15= 2

1. Core Subtraction Fact: 17 − 15 = 2

2. Inverse Addition Proof: 2 + 15 = 17 ✅

4−3= 1

1. Core Subtraction Fact: 4 − 3 = 1

2. Inverse Addition Proof: 1 + 3 = 4 ✅

11−6= 5

1. Core Subtraction Fact: 11 − 6 = 5

2. Inverse Addition Proof: 5 + 6 = 11 ✅

19−6= 13

1. Core Subtraction Fact: 19 − 6 = 13

2. Inverse Addition Proof: 13 + 6 = 19 ✅

9−2= 7

1. Core Subtraction Fact: 9 − 2 = 7

2. Inverse Addition Proof: 7 + 2 = 9 ✅

10.

20−13= 7

1. Core Subtraction Fact: 20 − 13 = 7

2. Inverse Addition Proof: 7 + 13 = 20 ✅

PanMaths.com • Answer Key & SolutionsPage 2 of 2

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Worksheet Info

Categorygrade-1

Grade LevelGrade 1

DifficultyEasy, Medium, Hard, Sprint

Time5-10 min

CCSS CodeCCSS.MATH.CONTENT.1.OA.C.6

Skills Practiced

✓ Subtraction Facts within 20

Key Strategies

🔟 Get to 10 First (Back Down Through 10): For 15 − 7: Split 7 into 5 and 2. Subtract 15 − 5 = 10, then subtract 10 − 2 = 8!
🔄 Use Related Addition Facts: If you know 9 + 6 = 15, you instantly know 15 − 6 = 9 and 15 − 9 = 6.
🤝 Half of Doubles Facts: Remember your doubles: 16 − 8 = 8, 14 − 7 = 7, 12 − 6 = 6.

🎮 Interactive Warm-Up

Subtraction Mastery

Warm up with 60 seconds of rapid mental math practice before printing!

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Related Worksheets

📄 Counting Objects (1–20)View →📄 Number Line Hops (Within 20)View →📄 Number Bonds to 10View →📄 Number Bonds to 20View →

📜 Standard: CCSS.MATH.CONTENT.1.OA.C.6🔗 CCSS.MATH.CONTENT.1.OA.B.4🔗 CCSS.MATH.CONTENT.1.OA.A.1

Mastering Subtraction Facts within 20: Core Concepts & Mental Models

Subtracting from teen numbers (11 to 20) introduces the crucial mental math strategy of 'Decomposing to Ten'. For 14 − 6, first subtract 4 to reach 10, then subtract the remaining 2 to reach 8. This eliminates the need for fingers and lays the groundwork for multi-digit column borrowing.

Worked Example & SolutionTeacher Step-by-Step Method

📝 Problem: Solve: 13 − 5 = ?

Worked Solution: 1. Back down through 10: 13 − 3 = 10. 2. Remaining to subtract: 5 − 3 = 2. 3. 10 − 2 = 8. (Proof: 8 + 5 = 13 ✅).

💡 Essential Strategies for Subtraction Facts within 20

🔟 Get to 10 First (Back Down Through 10)

For 15 − 7: Split 7 into 5 and 2. Subtract 15 − 5 = 10, then subtract 10 − 2 = 8!

🔄 Use Related Addition Facts

If you know 9 + 6 = 15, you instantly know 15 − 6 = 9 and 15 − 9 = 6.

🤝 Half of Doubles Facts

Remember your doubles: 16 − 8 = 8, 14 − 7 = 7, 12 − 6 = 6.

⚠️ Common Mistakes & Teacher Fixes

⚠️Stopping at 10 and forgetting the second step

Why students stumble: For 14 − 6, student subtracts 4 to reach 10 and writes 10 as the answer.

Teacher Fix: Always check: 'You only subtracted 4, but you needed to subtract 6! Subtract 2 more from 10.'

Example: 14 − 6 = 8, not 10.

📖 Key Mathematical Vocabulary

Teen Number

A number from 11 to 19 made of one group of ten and some extra ones.

Decompose Leading to 10

Splitting the subtrahend into two parts to reach 10 as an intermediate landmark.

🎯 4 Differentiated Classroom Sets Included

Standard 10Version A

Set A: Core Subtraction to 20 (10 Problems)

Teen subtraction facts bridging 10 with worked intermediate proofs.

Anti-CheatVersion B

Set B: Alternate Numbers (10 Problems)

Identical structure with alternate number combinations to prevent desk-copying.

ChallengingVersion C

Set C: Review & Fluency (8 Problems)

Mixed subtraction facts within 20 testing mental bridging strategies.

Speed SprintVersion D

Set D: 3-Minute Fluency Sprint (15 Problems)

15 rapid subtraction problems to evaluate speed, automaticity, and accuracy.

❓ Frequently Asked Questions

How do you solve a subtraction facts within 20 problem step by step?

Here is a worked example: "Solve: 13 − 5 = ?". Solution: 1. Back down through 10: 13 − 3 = 10. 2. Remaining to subtract: 5 − 3 = 2. 3. 10 − 2 = 8. (Proof: 8 + 5 = 13 ✅).

What is the core learning objective for subtraction facts within 20?

Subtract within 20, demonstrating fluency for subtraction within 10 and using strategies such as decomposing a number leading to a ten. This directly aligns with Common Core Standard CCSS.MATH.CONTENT.1.OA.C.6.

What is the most common mistake students make with subtraction facts within 20?

A frequent pitfall is: "Stopping at 10 and forgetting the second step". Why students stumble: For 14 − 6, student subtracts 4 to reach 10 and writes 10 as the answer. How to fix it: Always check: 'You only subtracted 4, but you needed to subtract 6! Subtract 2 more from 10.' (Example: 14 − 6 = 8, not 10.)

What is included in the 4 differentiated worksheet sets?

Set A covers standard core practice (Teen subtraction facts bridging 10 with worked intermediate proofs.). Set B is an Anti-Cheat version with alternate numbers to prevent copying. Set C features challenging problems, and Set D is a timed sprint.

Are these subtraction facts within 20 worksheets free to print with answer keys?

Yes! Every single worksheet on PanMaths is 100% free with no sign-up needed. Each sheet includes a dedicated Answer Key on Page 2 with step-by-step intermediate evaluation lines for 1-minute grading.