Relate addition and subtraction sentences

key notes :

Understanding Relationships:

  • Addition and subtraction are related operations.
  • They can be seen as opposite processes; addition combines numbers, while subtraction finds the difference between numbers.

Fact Families:

A set of numbers (e.g., 3, 5, and 8) can create multiple addition and subtraction sentences.

Example:

  • Addition: 3 + 5 = 8, 5 + 3 = 8
  • Subtraction: 8 – 3 = 5, 8 – 5 = 3

Part-Part-Whole Model:

  • Visualize numbers using models to show how parts come together to make a whole.
  • Example: If 2 and 4 are parts, 6 is the whole (2 + 4 = 6).

Using Number Lines:

  • Demonstrate how moving forward on a number line represents addition and moving backward shows subtraction.

Word Problems:

  • Practice with simple stories to connect addition and subtraction in real-life situations.
  • Example: “If you have 5 apples and give away 2, how many are left?”

Connecting Sentences:

  • Encourage students to write related addition and subtraction sentences.
  • Example: If 7 + 2 = 9, then 9 – 2 = 7.

Learn with an example

🍡If 7 + 1 = 8, then… ______− 7 = 1​

You can use fact families. A fact family is two addition number sentences and two subtraction number sentences that all use the same three numbers.

This is the fact family for 7 + 1 = 8:

  • 7 + 1 = 8
  • 1 + 7 = 8
  • 8 − 1 = 7
  • 8 − 7 = 1

Use the last fact. The number 8 must go in the blank space.

🍡If 7 + 1 = 8, then… 8 −_____  = 7

You can use fact families. A fact family is two addition number sentences and two subtraction number sentences that all use the same three numbers.

This is the fact family for 7 + 1 = 8:

7 + 1 = 8
1 + 7 = 8
8 − 7 = 1
8 − 1 = 7

Use the last fact. The number 1 must go in the blank space.

🍡If 2 + 3 = 5, then… − 3 = 2​

You can use fact families. A fact family is two addition number sentences and two subtraction number sentences that all use the same three numbers.

This is the fact family for 2 + 3 = 5:

2 + 3 = 5
3 + 2 = 5
5 − 2 = 3
5 − 3 = 2

Use the last fact. The number 5 must go in the blank space.

Let’s practice!