Estimating the addition worksheet for rounding numbers to the nearest ten.

You're working on a worksheet titled “Estimating the Addition”, which asks you to:

> Round each whole number to the nearest ten, then add the rounded numbers.

This is an estimation exercise — not exact calculation — so we’re practicing rounding and mental math.

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🔢 How to Round to the Nearest Ten:

- Look at the ones digit (the last digit).
- If it’s 0–4, round down.
- If it’s 5–9, round up.
- Then add the two rounded numbers.

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Let’s solve all 20 problems step by step.

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✔ Problem 1:

45 → 50 (5 in ones → round up)
23 → 20 (3 in ones → round down)
50 + 20 = 70 ← Already filled in ✔

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✔ Problem 2:

75 → 80 (5 → round up)
48 → 50 (8 → round up)
80 + 50 = 130

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✔ Problem 3:

66 → 70 (6 → round up)
23 → 20 (3 → round down)
70 + 20 = 90

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✔ Problem 4:

55 → 60 (5 → round up)
42 → 40 (2 → round down)
60 + 40 = 100

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✔ Problem 5:

73 → 70 (3 → round down)
45 → 50 (5 → round up)
70 + 50 = 120

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✔ Problem 6:

89 → 90 (9 → round up)
33 → 30 (3 → round down)
90 + 30 = 120

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✔ Problem 7:

23 → 20 (3 → round down)
45 → 50 (5 → round up)
20 + 50 = 70

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✔ Problem 8:

76 → 80 (6 → round up)
37 → 40 (7 → round up)
80 + 40 = 120

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✔ Problem 9:

34 → 30 (4 → round down)
25 → 30 (5 → round up)
30 + 30 = 60

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✔ Problem 10:

46 → 50 (6 → round up)
39 → 40 (9 → round up)
50 + 40 = 90

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✔ Problem 11:

76 → 80 (6 → round up)
25 → 30 (5 → round up)
80 + 30 = 110

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✔ Problem 12:

78 → 80 (8 → round up)
23 → 20 (3 → round down)
80 + 20 = 100

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✔ Problem 13:

67 → 70 (7 → round up)
39 → 40 (9 → round up)
70 + 40 = 110

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✔ Problem 14:

22 → 20 (2 → round down)
17 → 20 (7 → round up)
20 + 20 = 40

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✔ Problem 15:

67 → 70 (7 → round up)
34 → 30 (4 → round down)
70 + 30 = 100

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✔ Problem 16:

85 → 90 (5 → round up)
49 → 50 (9 → round up)
90 + 50 = 140

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✔ Problem 17:

89 → 90 (9 → round up)
33 → 30 (3 → round down)
90 + 30 = 120

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✔ Problem 18:

67 → 70 (7 → round up)
33 → 30 (3 → round down)
70 + 30 = 100

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✔ Problem 19:

56 → 60 (6 → round up)
32 → 30 (2 → round down)
60 + 30 = 90

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✔ Problem 20:

87 → 90 (7 → round up)
67 → 70 (7 → round up)
90 + 70 = 160

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## 📝 Final Answers (Fill in the blanks):

| Problem | Rounded Numbers | Estimated Sum |
|---------|----------------------|---------------|
| 1 | 50 + 20 | 70 |
| 2 | 80 + 50 | 130 |
| 3 | 70 + 20 | 90 |
| 4 | 60 + 40 | 100 |
| 5 | 70 + 50 | 120 |
| 6 | 90 + 30 | 120 |
| 7 | 20 + 50 | 70 |
| 8 | 80 + 40 | 120 |
| 9 | 30 + 30 | 60 |
| 10 | 50 + 40 | 90 |
| 11 | 80 + 30 | 110 |
| 12 | 80 + 20 | 100 |
| 13 | 70 + 40 | 110 |
| 14 | 20 + 20 | 40 |
| 15 | 70 + 30 | 100 |
| 16 | 90 + 50 | 140 |
| 17 | 90 + 30 | 120 |
| 18 | 70 + 30 | 100 |
| 19 | 60 + 30 | 90 |
| 20 | 90 + 70 | 160 |

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✔ You can now fill in all the blanks with these estimated sums!

Why this matters: Estimation helps you quickly check if your exact answer is reasonable. For example, if you calculate 75 + 48 exactly and get 123, your estimate of 130 tells you you’re close — good job!

Let me know if you’d like to compare estimated vs. exact answers too! 😊