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Contributor: Erika Wargo. Lesson ID: 12405
Just like people, numbers have families. Some numbers belong together and help you with addition and subtraction! Learn to solve (and write) number sentences with interactives. Don't duck out on us!
8 ducklings were in the pond when 7 more ducklings joined them. How many ducklings are in the pond? If 4 fly away, how many are left? Don't "quack up" trying to figure out the answers; we'll show you how to solve fact problems!
Addition is combining two or more groups into one group.
The answer to an addition problem is called the sum. An addition number sentence can be written vertically or horizontally. A number sentence uses numbers and symbols instead of words.
Two ways to show addition are shown below. When we add two numbers, the order doesn’t matter. Either number can be written first.
horizontally
5 + 3 = 8
3 + 5 = 8
vertically
| 5 |
| + 3 |
| 8 |
| 3 |
| + 5 |
| 8 |
Subtraction is separating one group into two groups. The answer to a subtraction problem is called the difference. A subtraction number sentence can also be written vertically or horizontally. However, the order of numbers matters in subtraction. The number with the greater value is written first when solving most subtraction problems.
horizontally
8 - 3 = 5
8 - 5 = 3
vertically
| 8 |
| - 3 |
| 5 |
| 8 |
| - 5 |
| 3 |
A subtraction problem can be checked by adding the difference to the number subtracted. Think of doing the problem “in reverse.”
4 + 6 = 10, so 10 - 6 = 4
6 + 4 = 10, so 10 - 4 = 6
Addition and subtraction facts form fact families, groups of three numbers that are arranged to form number sentences. Fact families help us learn facts and allow us to improve at solving math problems.
As you watch a Discovery Education video about Fact Families, see if you can find the answer to this question:
How are addition and subtraction fact families related? Discuss with a parent or teacher.
Create an addition and subtraction fact family from the numbers 4, 6, and 10, and share with a parent or teacher.
In the Got It? section, you will practice adding and subtracting numbers as you play an online game and complete an interactive quiz.
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