Let's solve the estimation addition problems by
rounding each number to the nearest ten, then adding the rounded numbers. This is a common method for estimating sums quickly.
We'll go through each problem step by step.
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Problem 1: 53 + 12
- Round 53 → 50 (nearest ten)
- Round 12 → 10 (nearest ten)
- Estimate: 50 + 10 =
60 ✔
(Already given as correct.)
---
Problem 2: 79 + 24
- Round 79 → 80
- Round 24 → 20
- Estimate: 80 + 20 =
100
---
Problem 3: 42 + 17
- Round 42 → 40
- Round 17 → 20
- Estimate: 40 + 20 =
60
---
Problem 4: 31 + 62
- Round 31 → 30
- Round 62 → 60
- Estimate: 30 + 60 =
90
---
Problem 5: 87 + 47
- Round 87 → 90
- Round 47 → 50
- Estimate: 90 + 50 =
140
---
Problem 6: 25 + 18
- Round 25 → 30
- Round 18 → 20
- Estimate: 30 + 20 =
50
---
Problem 7: 45 + 97
- Round 45 → 50
- Round 97 → 100
- Estimate: 50 + 100 =
150
---
Problem 8: 38 + 64
- Round 38 → 40
- Round 64 → 60
- Estimate: 40 + 60 =
100
---
Problem 9: 55 + 55
- Round 55 → 60
- Round 55 → 60
- Estimate: 60 + 60 =
120
---
Problem 10: 11 + 99
- Round 11 → 10
- Round 99 → 100
- Estimate: 10 + 100 =
110
---
Problem 11: 28 + 43
- Round 28 → 30
- Round 43 → 40
- Estimate: 30 + 40 =
70
---
Problem 12: 82 + 29
- Round 82 → 80
- Round 29 → 30
- Estimate: 80 + 30 =
110
---
Problem 13: 15 + 63
- Round 15 → 20
- Round 63 → 60
- Estimate: 20 + 60 =
80
---
Problem 14: 34 + 74
- Round 34 → 30
- Round 74 → 70
- Estimate: 30 + 70 =
100
---
Problem 15: 24 + 90
- Round 24 → 20
- Round 90 → 90 (already a multiple of ten)
- Estimate: 20 + 90 =
110
---
✔ Final Answers:
| Problem | Rounded Sum |
|--------|-------------|
| 53 + 12 → 50 + 10 =
60 | ✔️ Given |
| 79 + 24 → 80 + 20 =
100 |
| 42 + 17 → 40 + 20 =
60 |
| 31 + 62 → 30 + 60 =
90 |
| 87 + 47 → 90 + 50 =
140 |
| 25 + 18 → 30 + 20 =
50 |
| 45 + 97 → 50 + 100 =
150 |
| 38 + 64 → 40 + 60 =
100 |
| 55 + 55 → 60 + 60 =
120 |
| 11 + 99 → 10 + 100 =
110 |
| 28 + 43 → 30 + 40 =
70 |
| 82 + 29 → 80 + 30 =
110 |
| 15 + 63 → 20 + 60 =
80 |
| 34 + 74 → 30 + 70 =
100 |
| 24 + 90 → 20 + 90 =
110 |
---
📝 Explanation:
To estimate the sum:
1.
Round each addend 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 and reasonable estimate of the actual sum.
For example:
- 79 → 80 (since 9 ≥ 5)
- 24 → 20 (since 4 < 5)
- So 79 + 24 ≈ 80 + 20 = 100
This method helps in mental math and checking if answers are reasonable.
Let me know if you'd like the actual exact sums too!
Parent Tip: Review the logic above to help your child master the concept of estimation and rounding worksheet.
