Estimation: Sum or Difference worksheet with rounding exercises.

It looks like you've uploaded a worksheet titled "Estimation: Sum or Difference" from the A+ Math series, where students are asked to estimate sums or differences by rounding numbers to the nearest ten. The goal is to practice estimation skills using basic rounding rules.

Let’s go through each problem step-by-step and solve them with explanations.

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🔹 Rounding Rule Reminder:

- If the ones digit is 5 or more, round up.
- If the ones digit is less than 5, round down.

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✔ Problem 1:

56 + 34 → ?

- Round 56: ones digit is 6 → round up → 60
- Round 34: ones digit is 4 → round down → 30
- Estimate: 60 + 30 = 90

✔ Answer: 60 + 30 = 90

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✔ Problem 2:

880 – 126 → ?

- Round 880: already ends in 0 → stays 880
- Round 126: ones digit is 6 → round up → 130
- Estimate: 880 – 130 = 750

✔ Answer: 880 – 130 = 750

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✔ Problem 3:

901 – 49 → ?

- Round 901: ones digit is 1 → round down → 900
- Round 49: ones digit is 9 → round up → 50
- Estimate: 900 – 50 = 850

✔ Answer: 900 – 50 = 850

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✔ Problem 4:

72 – 46 → ?

- Round 72: ones digit is 2 → round down → 70
- Round 46: ones digit is 6 → round up → 50
- Estimate: 70 – 50 = 20

✔ Answer: 70 – 50 = 20

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✔ Problem 5:

258 + 360 → ?

- Round 258: ones digit is 8 → round up → 260
- Round 360: already ends in 0 → stays 360
- Estimate: 260 + 360 = 620

✔ Answer: 260 + 360 = 620

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✔ Problem 6:

79 + 71 → ?

- Round 79: ones digit is 9 → round up → 80
- Round 71: ones digit is 1 → round down → 70
- Estimate: 80 + 70 = 150

✔ Answer: 80 + 70 = 150

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✔ Problem 7:

533 + 360 → ?

- Round 533: ones digit is 3 → round down → 530
- Round 360: already ends in 0 → stays 360
- Estimate: 530 + 360 = 890

✔ Answer: 530 + 360 = 890

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✔ Problem 8:

548 – 186 → ?

- Round 548: ones digit is 8 → round up → 550
- Round 186: ones digit is 6 → round up → 190
- Estimate: 550 – 190 = 360

✔ Answer: 550 – 190 = 360

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✔ Problem 9:

444 – 22 → ?

- Round 444: ones digit is 4 → round down → 440
- Round 22: ones digit is 2 → round down → 20
- Estimate: 440 – 20 = 420

✔ Answer: 440 – 20 = 420

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✔ Problem 10:

931 + 210 → ?

- Round 931: ones digit is 1 → round down → 930
- Round 210: already ends in 0 → stays 210
- Estimate: 930 + 210 = 1,140

✔ Answer: 930 + 210 = 1,140

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📝 Final Answers Summary:

| Problem | Rounded Numbers | Estimated Result |
|--------|------------------|------------------|
| 1) | 60 + 30 | 90 |
| 2) | 880 – 130 | 750 |
| 3) | 900 – 50 | 850 |
| 4) | 70 – 50 | 20 |
| 5) | 260 + 360 | 620 |
| 6) | 80 + 70 | 150 |
| 7) | 530 + 360 | 890 |
| 8) | 550 – 190 | 360 |
| 9) | 440 – 20 | 420 |
| 10) | 930 + 210 | 1,140 |

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✔ How to Fill in the Worksheet:

For each problem, write the rounded numbers in the ovals, then compute the estimated sum/difference in the final oval.

Example for Problem 1:
```
56 → [60]
34 → [30]
→ [90]
```

Repeat this format for all problems.

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