1st Grade Subtraction Within 20 Worksheet
Practice subtraction within 20, using a number line to count back or count up to the answer.
- Homework
- Morning Work
- Centers
- Review
- Intervention
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No sign-up required. Clean, low-ink US Letter format.
- Grade
- 1st Grade
- Subject
- Math
- Skill
- Subtraction
- Topic
- subtraction facts within 20
- Difficulty
- Standard
- Time
- 12 minutes
- Pages
- 2 (incl. answer key)
- Format
- Printable PDF (US Letter)
- Answer key
- Included
- Best for
- homework, morning work, centers, review, intervention
Worksheet details
What This Worksheet Practices
Students will subtract within 20 using counting back or counting up on a number line.
- Subtracting within 20
- Counting back on a number line
- Counting up to find a difference
Worksheet Preview
Two ways to subtract within 20
Subtraction is easier when students can choose the smarter strategy. Count back when you’re taking away a small amount (15 − 3). Count up when the two numbers are close (15 − 12 is just three hops up from 12). Teaching both — and letting students pick the shorter path — builds real number sense rather than one rigid procedure.
How to use it
Lean on the number line. For counting back, start at the bigger number and hop left. For counting up, start at the smaller number and hop right until you reach the bigger one — the number of hops is the answer. Watch for the classic off-by-one error of counting the starting number itself. Pair with addition within 20 to connect the two operations.
👩🏫 Teacher note
Show both strategies: count back (15 - 3) and count up (15 - 12 is easier counting up from 12). Let students pick the shorter hop.
🏠 Parent note
For 15 - 3, start at 15 and hop back 3. For 15 - 12, count up from 12 to 15 instead — it's quicker.
Common Mistakes to Watch For
- Counting back but including the starting number
- Subtracting the larger number from the smaller out of habit
Answer Key
Each answer shows the difference.
⬇ Download Answer Key (PDF)Part of a Practice Pack
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