Let's solve the worksheet step by step.
Task:
Estimate the addition by
rounding each whole number to the nearest ten, then add the rounded numbers.
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We'll go through each problem one by one.
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1. 77 + 33
- Round 77 → 80 (since 77 is closer to 80 than 70)
- Round 33 → 30 (since 33 is closer to 30 than 40)
- Add: 80 + 30 =
110
✔ Already given as an example.
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2. 45 + 34
- Round 45 → 50 (closer to 50 than 40)
- Round 34 → 30 (closer to 30 than 40)
- Add: 50 + 30 =
80
Answer:
50 + 30 = 80
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3. 54 + 33
- Round 54 → 50 (closer to 50 than 60)
- Round 33 → 30
- Add: 50 + 30 =
80
Answer:
50 + 30 = 80
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4. 23 + 32
- Round 23 → 20
- Round 32 → 30
- Add: 20 + 30 =
50
Answer:
20 + 30 = 50
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5. 45 + 23
- Round 45 → 50
- Round 23 → 20
- Add: 50 + 20 =
70
Answer:
50 + 20 = 70
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6. 67 + 32
- Round 67 → 70
- Round 32 → 30
- Add: 70 + 30 =
100
Answer:
70 + 30 = 100
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7. 81 + 23
- Round 81 → 80
- Round 23 → 20
- Add: 80 + 20 =
100
Answer:
80 + 20 = 100
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8. 45 + 65
- Round 45 → 50
- Round 65 → 70
- Add: 50 + 70 =
120
Answer:
50 + 70 = 120
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9. 65 + 23
- Round 65 → 70
- Round 23 → 20
- Add: 70 + 20 =
90
Answer:
70 + 20 = 90
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10. 45 + 22
- Round 45 → 50
- Round 22 → 20
- Add: 50 + 20 =
70
Answer:
50 + 20 = 70
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✔ Final Answers:
| Problem | Rounded Addition | Estimated Sum |
|--------|------------------|----------------|
| 1. | 80 + 30 | 110 |
| 2. | 50 + 30 | 80 |
| 3. | 50 + 30 | 80 |
| 4. | 20 + 30 | 50 |
| 5. | 50 + 20 | 70 |
| 6. | 70 + 30 | 100 |
| 7. | 80 + 20 | 100 |
| 8. | 50 + 70 | 120 |
| 9. | 70 + 20 | 90 |
| 10. | 50 + 20 | 70 |
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🔍 Explanation:
To estimate sums:
1.
Round each number to the nearest ten.
- If the ones digit is 5 or more, round up.
- If it's less than 5, round down.
2.
Add the rounded numbers.
3. This gives a quick, approximate answer useful for checking reasonableness.
For example:
- 45 → 50 (ones digit is 5 → round up)
- 23 → 20 (ones digit is 3 → round down)
Then 50 + 20 = 70.
This method helps in mental math and checking if exact answers are reasonable.
✔ All problems solved!
Parent Tip: Review the logic above to help your child master the concept of estimation worksheet for 3rd grade.
