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Add & Subtract Within 20
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What you will learn from this videoWhat you will learn
- We’ll learn how to add and subtract numbers up to 20.
- We'll also learn how to solve addition and subtraction problems with a missing number.
- And we’ll discover that this knowledge can help us win trophies, feed animals, and even decorate gingerbread houses!
- Discussion Questions
Before Video
How can you count all to add 6 + 3?ANSWERCount 1, 2, 3, 4, 5, 6, 7, 8, 9. So 6 + 3 = 9.
Start at 4. Then count on 2 more: 5, 6. So 4 + 2 = 6. Or, start at 2. Then count on 4 more. 3, 4, 5, 6. So 4 + 2 = 6.
Start at 7. Then count back 5: 6, 5, 4, 3, 2. So 7 – 5 = 2.
Start at 7. Then count on to 9. 8, 9. I counted 2, so 9 – 7 = 2.
6 + 2 = 8. There are 8 dogs in all.
After Video
How can you add 5 + 9?ANSWERYou could count all, count on from 5, or count on from 9. 5 + 9 = 14.
I can count on to find the missing number. Start at 9 and count on to 12. I put up one finger for each number I count. 10, 11, 12. I put up 3 fingers, which means I counted on 3. So, the missing number is 3.
I could count back from 15 or count on from 3. 15 – 3 = 12.
I can count back to find the missing number. Start at 19 and count back to 14. To keep track on my fingers, I put up one finger for each number I count. 18, 17, 16, 15, 14. I put up 5 fingers, so I counted back 5. So, the missing number is 5.
14 – ? = 9. Start from 14. Then, count back to 9. 13, 12, 11, 10, 9. I counted back 5 numbers, so the missing number is 5. I gave away 5 stickers.
- Vocabulary
- Add DEFINE
To put together.
- Subtract DEFINE
To take away.
- Count all DEFINE
To count every object. One way to add is to count all.
- Count on DEFINE
To count in increasing order. You can use counting on to solve addition and subtraction problems. For example, you can add 6 + 3 by starting from 6 and then counting on 3: 7, 8, 9.
- Count back DEFINE
To count in decreasing order. You can use counting back to solve addition and subtraction problems. For example, you can subtract 6 – 3 by starting from 6 and then counting back 3: 5, 4, 3.
- Difference DEFINE
The result of subtracting.
- Sum DEFINE
The result of adding.
- Add DEFINE
- Reading Material
- Practice Word Problems
- Practice Number Problems
- Lesson Plan
- Teacher Guide