R.3 Subtract by counting forward - up to 20
What does subtraction mean?
Subtraction means taking away from a group or finding how many are left.
- You have 10 apples. You give away 3 apples.
- 10 − 3 = 7
- There are 7 apples left.
Subtraction helps you find the answer when something is taken away.
What is counting forward?
Counting forward means starting at one number and counting up to another number.
- Start at 5 and count to 8: 6, 7, 8
- You counted 3 numbers.
Counting forward helps you find how many more you need to reach a number.
Subtracting by counting forward
Subtracting by counting forward means starting with the smaller number and counting up to the larger number to find the difference.
- 12 − 9 = ?
- Start at 9 and count forward to 12:
- 10, 11, 12
- You counted 3 numbers.
- So, 12 − 9 = 3
This strategy works best when the numbers are close together.
Using a number line to count forward
A number line shows numbers in order and can help you count forward to subtract.
- 15 − 11 = ?
- Start at 11 on the number line.
- Jump forward to 15.
- Count the jumps: 12, 13, 14, 15
- You made 4 jumps.
- So, 15 − 11 = 4
Each jump on the number line counts as one.
Checking your subtraction
You can check subtraction by adding to see if you get the larger number.
- 14 − 10 = 4
- Check: 10 + 4 = 14
- The answer is correct.
If your addition matches the larger number, your subtraction is correct.
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. Students use counting forward as a strategy to subtract within 20.
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