⭐ 1st Grade · Free printable

Subtraction Within 20 Worksheets

Subtraction within 20 is where many children get stuck counting back by ones. Two strategies make it much easier.

Think addition: to find 13 − 9, ask "9 plus what makes 13?" Subtract back to ten: to find 14 − 6, first take 4 to get to 10, then take the other 2 to get 8. Every starting number on these worksheets is 20 or less.

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Choose how many problems. Every worksheet has new problems and a matching answer key.

Opens in a new tab, ready to print. Use the Answer Key button there to print the answers.

Sample problems

  1. 11 − 7 = _____
  2. 15 − 5 = _____
  3. 6 − 5 = _____
  4. 20 − 10 = _____
  5. 16 − 12 = _____
  6. 10 − 8 = _____
  7. 10 − 3 = _____
  8. 20 − 7 = _____

Worked example

13 − 5

  1. Split the 5 into 3 and 2, because 13 − 3 lands exactly on 10.
  2. 13 − 3 = 10.
  3. Take away the other 2: 10 − 2 = 8.
  4. So 13 − 5 = 8.

Common mistakes

  • Off-by-one errors when counting back, from saying the starting number as the first count. The first count back from 13 is 12.
  • Turning the problem around in their head, thinking "you can't take 13 from 5" and giving up. The first number is always the starting amount.

Tips for practicing at home

  • Use fact family triangles: 5, 8 and 13 make 5 + 8, 8 + 5, 13 − 5 and 13 − 8.
  • Encourage "think addition" out loud: "8 plus what makes 13?"
  • Play with dominoes: the total dots minus one side equals the other side.

Common Core standards

1.OA.C.6
Add and subtract within 20, demonstrating fluency for addition and subtraction within 10.
1.OA.B.4
Understand subtraction as an unknown-addend problem: subtract 10 − 8 by finding the number that makes 10 when added to 8.

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