U.1 Use addition and subtraction to make numbers - up to 20
What does it mean to make numbers?
Making numbers means joining (adding) or separating (subtracting) smaller numbers to get a number up to 20.
- 7 and 3 make 10.
- 12 is 10 and 2 more.
- 15 is 10 and 5 more.
Many numbers can be made in more than one way.
Using addition to make numbers
Addition means putting groups together to find how many in all.
- 6 + 4 = 10
- 8 + 2 = 10
- 9 + 6 = 15
Counting on from the bigger number helps you add faster.
Using subtraction to make numbers
Subtraction means taking away from a group to find how many are left.
- 10 − 3 = 7
- 14 − 4 = 10
- 18 − 8 = 10
Think: “How many are left after some go away?”
Make a ten strategy
Sometimes it is easier to add by first making 10 and then adding the rest.
- 8 + 5 → 8 + 2 = 10, then 10 + 3 = 13
- 9 + 7 → 9 + 1 = 10, then 10 + 6 = 16
Making 10 first helps your brain solve problems quickly.
Fact families
Fact families are addition and subtraction facts that use the same three numbers.
- 3 + 7 = 10
- 7 + 3 = 10
- 10 − 3 = 7
- 10 − 7 = 3
If you know one fact, you can find the others.
Solving story problems
Read the story to decide if you should add or subtract to find the answer.
- Sam has 9 apples. He gets 4 more. How many now? → 9 + 4 = 13
- Maria has 15 balloons. 5 fly away. How many left? → 15 − 5 = 10
Words like more often mean add. Words like left often mean subtract.
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, independent practice, or homework.
All content is 100% free, student-safe, and designed for classroom and home use.