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K.2 Addition and subtraction sentences that match - up to 10

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Understanding Subtraction

Subtraction means taking away from a group to find out how many are left. It shows the difference between two numbers.

Examples:
  • Problem: 5 − 2 = ?
    Solution: Start with 5 objects. Take away 2. 3 are left. So, 5 − 2 = 3.
  • Problem: 4 − 1 = ?
    Solution: Start with 4. Take away 1. 3 are left. So, 4 − 1 = 3.
Helpful Hint

Think of subtraction as “taking away” or “finding what is left.”

Counting Back to Subtract

Counting back is a way to subtract by starting at a number and saying the numbers in reverse order. Each number you say takes one away.

Examples:
  • Problem: 7 − 2 = ?
    Solution: Start at 7. Count back two numbers: 6, 5. So, 7 − 2 = 5.
  • Problem: 9 − 3 = ?
    Solution: Start at 9. Count back three numbers: 8, 7, 6. So, 9 − 3 = 6.
Helpful Hint

Always move to smaller numbers one step at a time when counting back.

Using Fingers to Subtract

Fingers can help us keep track of how many we subtract. Show the starting number in your head, then fold down one finger for each count back.

Examples:
  • Problem: 6 − 2 = ?
    Solution: Start at 6 in your head. Fold down 1 finger (5), then another (4). So, 6 − 2 = 4.
  • Problem: 8 − 3 = ?
    Solution: Start at 8. Fold down 3 fingers: 7, 6, 5. So, 8 − 3 = 5.
Helpful Hint

Say each number out loud as you fold down a finger to avoid skipping steps.

Using Number Bonds

A number bond shows how a number can be broken into parts. Subtraction can be thought of as taking away one part to find the other.

Examples:
  • Problem: 7 − 4 = ?
    Solution: 7 can be split into 4 and 3. If we take away 4, the other part is 3. So, 7 − 4 = 3.
  • Problem: 5 − 2 = ?
    Solution: 5 can be split into 2 and 3. If we take away 2, the other part is 3. So, 5 − 2 = 3.
Helpful Hint

Number bonds help us see the connection between addition and subtraction.

Making Ten to Subtract

Sometimes it helps to think about making ten. Break apart a number to subtract more easily.

Examples:
  • Problem: 10 − 3 = ?
    Solution: Start at 10. Take away 3. 7 are left. So, 10 − 3 = 7.
  • Problem: 9 − 5 = ?
    Solution: Think of 9 as 5 and 4. Take away 5, leaving 4. So, 9 − 5 = 4.
Helpful Hint

Breaking numbers apart can make subtraction faster and easier.

Connecting Addition and Subtraction

Addition and subtraction are related. If you know one, you can find the other. These pairs are called fact families.

Examples:
  • Problem: If 6 + 2 = 8, then 8 − 2 = ?
    Solution: If 6 + 2 makes 8, then 8 − 2 must equal 6.
  • Problem: If 4 + 5 = 9, then 9 − 5 = ?
    Solution: If 4 + 5 makes 9, then 9 − 5 must equal 4.
Helpful Hint

Every addition sentence has a matching subtraction sentence in its fact family.

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