S.3 Use subtraction to make numbers - up to 20
What is subtraction?
Subtraction means taking away from a group to find how many are left. It helps us compare amounts and solve everyday problems.
- You have 8 apples.
- You give away 3 apples.
- Now you have 5 apples left.
Subtraction answers tell how many are left or how many are missing.
Subtraction using numbers up to 20
In first grade, students learn to subtract numbers within 20. This means the starting number is 20 or less.
- 10 − 2 = 8
- 15 − 5 = 10
- 20 − 1 = 19
Make sure the first number is bigger than the number you subtract.
Using objects to subtract
You can use objects, drawings, or pictures to help you subtract. This makes subtraction easier to understand.
- Draw 6 stars.
- Cross out 2 stars.
- Count the stars left: 4.
Using objects helps you see what is being taken away.
Subtraction sentences
A subtraction sentence shows subtraction using numbers and symbols.
- 9 − 4 = 5
- 12 − 7 = 5
- 18 − 10 = 8
The minus sign (−) means take away.
Using subtraction to make numbers
You can use subtraction to make a number by taking away from a larger number.
- To make 6: 10 − 4 = 6
- To make 9: 14 − 5 = 9
- To make 12: 20 − 8 = 12
Think about what number needs to be taken away to reach the answer.
Common Core alignment: CCSS.MATH.CONTENT.1.OA.C.6 – Add and subtract within 20.
Notes for teachers
This free lesson is aligned with CCSS.MATH.CONTENT.1.OA.C.6. Use it for whole-class instruction, small groups, or independent practice.
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