Resources/Addition and subtraction within 20
K to Grade 1•Printable worksheet + answer key•CC0 license

Addition and subtraction within 20

A printable lesson for building fluency with small numbers.

Students practice adding and subtracting within 20 using number lines and ten frames.

Print-ready worksheet with answer key and quick teaching tips.

K to Grade 10 problems10 minAnswer key included
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Ready-to-teach

Clear steps, examples, and practice in one printable page.

Misconception-proof

Highlights common mistakes and how to fix them quickly.

Open license

CC0: free to copy, adapt, and share without attribution.

Quick overview

This free addition and subtraction worksheet for kindergarten and grade 1 builds fluency within 20.

Lesson plan snapshot

10-15 min
  • Warm-up (2 min): count on with a number line.
  • Model (3 min): solve the worked example together.
  • Guided practice (4 min): complete problems 1-3 as a group.
  • Independent practice (5 min): finish the remaining problems.

Materials: number line, ten frame

Learning targets

  • Add within 20 using counting on.
  • Subtract within 20 using counting back.
  • Explain strategies with visuals.

Step-by-step approach

  1. 1Start with the larger number.
  2. 2Count on for addition (4 + 3 means 4, 5, 6, 7).
  3. 3Count back for subtraction (9 - 2 means 8, 7).
  4. 4Check with a quick drawing or ten frame.

Common mistakes

Mistake

Starting from 1 instead of counting on.

Try instead

Start at the first number to save time and reduce errors.

Mistake

Mixing up the minus sign.

Try instead

Say “take away” when you see subtraction.

Mistake

Skipping numbers when counting.

Try instead

Point to the number line or use fingers to keep track.

Worked example

Guided
Solve: 8 - 3 = ?
  1. Start at 8.
  2. Count back 3 steps: 7, 6, 5.
Answer: 5

Related resources

Number bonds

Compose and decompose numbers within 10.

View resource

Counting

Count, compare, and write numbers to 20.

View resource

Skip counting

Count by 2s, 5s, and 10s.

View resource

Practice problems

10 problems • 15 min

Printable worksheet
  1. 1
    There are 37 candies. 5 are given away. How many are left?
  2. 2
    Add with regrouping: 49+4549 + 45
  3. 3
    Solve: 97−5597 - 55
  4. 4
    Solve: 66+6766 + 67
  5. 5
    Solve: 6+8+56 + 8 + 5
  6. 6
    Find the missing number: 78 - \text{___} = 34
  7. 7
    Sam has 16 marbles and finds 8 more. How many marbles does Sam have now?
  8. 8
    Solve: 87−1587 - 15
  9. 9
    Solve: 34+4834 + 48
  10. 10
    Solve: 2+82 + 8

Answer key

10 answers
  1. 11) 32
  2. 22) 94
  3. 33) 42
  4. 44) 133
  5. 55) 19
  6. 66) 44
  7. 77) 24
  8. 88) 72
  9. 99) 82
  10. 1010) 10

Teacher tips

  • TUse number lines and ten frames before mental strategies.
  • TEncourage students to explain their counting steps.
  • TFocus on accuracy before speed.

Parent tips

  • PPractice facts in short bursts (2-3 minutes).
  • PUse small objects like coins or blocks.
  • PAsk, “How did you get that?”

Open license

You are free to copy, adapt, and share these materials. No attribution required. Released under Creative Commons CC0 1.0 (public domain).