Estimating Sums Worksheets - 15 Worksheets Library - Free Printable

To solve the problem of estimating the addition by rounding each whole number to the nearest ten, we will follow these steps:

Steps:

1. Round each number to the nearest ten:
- If the ones digit is 5 or greater, round up.
- If the ones digit is less than 5, round down.

2. Add the rounded numbers:
- Perform the addition of the rounded numbers to get the estimated sum.

3. Write the results:
- Fill in the blanks with the rounded numbers and their sums.

Let's solve each problem step by step:

---

#### Problem 1:
$$
77 + 33
$$
- Round 77 to the nearest ten: \( 77 \rightarrow 80 \)
- Round 33 to the nearest ten: \( 33 \rightarrow 30 \)
- Add the rounded numbers: \( 80 + 30 = 110 \)

Answer:
$$
\boxed{80 + 30 = 110}
$$

---

#### Problem 2:
$$
45 + 34
$$
- Round 45 to the nearest ten: \( 45 \rightarrow 50 \)
- Round 34 to the nearest ten: \( 34 \rightarrow 30 \)
- Add the rounded numbers: \( 50 + 30 = 80 \)

Answer:
$$
\boxed{50 + 30 = 80}
$$

---

#### Problem 3:
$$
54 + 33
$$
- Round 54 to the nearest ten: \( 54 \rightarrow 50 \)
- Round 33 to the nearest ten: \( 33 \rightarrow 30 \)
- Add the rounded numbers: \( 50 + 30 = 80 \)

Answer:
$$
\boxed{50 + 30 = 80}
$$

---

#### Problem 4:
$$
23 + 32
$$
- Round 23 to the nearest ten: \( 23 \rightarrow 20 \)
- Round 32 to the nearest ten: \( 32 \rightarrow 30 \)
- Add the rounded numbers: \( 20 + 30 = 50 \)

Answer:
$$
\boxed{20 + 30 = 50}
$$

---

#### Problem 5:
$$
45 + 23
$$
- Round 45 to the nearest ten: \( 45 \rightarrow 50 \)
- Round 23 to the nearest ten: \( 23 \rightarrow 20 \)
- Add the rounded numbers: \( 50 + 20 = 70 \)

Answer:
$$
\boxed{50 + 20 = 70}
$$

---

#### Problem 6:
$$
67 + 32
$$
- Round 67 to the nearest ten: \( 67 \rightarrow 70 \)
- Round 32 to the nearest ten: \( 32 \rightarrow 30 \)
- Add the rounded numbers: \( 70 + 30 = 100 \)

Answer:
$$
\boxed{70 + 30 = 100}
$$

---

#### Problem 7:
$$
81 + 23
$$
- Round 81 to the nearest ten: \( 81 \rightarrow 80 \)
- Round 23 to the nearest ten: \( 23 \rightarrow 20 \)
- Add the rounded numbers: \( 80 + 20 = 100 \)

Answer:
$$
\boxed{80 + 20 = 100}
$$

---

#### Problem 8:
$$
45 + 65
$$
- Round 45 to the nearest ten: \( 45 \rightarrow 50 \)
- Round 65 to the nearest ten: \( 65 \rightarrow 70 \)
- Add the rounded numbers: \( 50 + 70 = 120 \)

Answer:
$$
\boxed{50 + 70 = 120}
$$

---

#### Problem 9:
$$
65 + 23
$$
- Round 65 to the nearest ten: \( 65 \rightarrow 70 \)
- Round 23 to the nearest ten: \( 23 \rightarrow 20 \)
- Add the rounded numbers: \( 70 + 20 = 90 \)

Answer:
$$
\boxed{70 + 20 = 90}
$$

---

#### Problem 10:
$$
45 + 22
$$
- Round 45 to the nearest ten: \( 45 \rightarrow 50 \)
- Round 22 to the nearest ten: \( 22 \rightarrow 20 \)
- Add the rounded numbers: \( 50 + 20 = 70 \)

Answer:
$$
\boxed{50 + 20 = 70}
$$

---

Final Answer:

$$
\boxed{
\begin{aligned}
1. & \quad 80 + 30 = 110 \\
2. & \quad 50 + 30 = 80 \\
3. & \quad 50 + 30 = 80 \\
4. & \quad 20 + 30 = 50 \\
5. & \quad 50 + 20 = 70 \\
6. & \quad 70 + 30 = 100 \\
7. & \quad 80 + 20 = 100 \\
8. & \quad 50 + 70 = 120 \\
9. & \quad 70 + 20 = 90 \\
10. & \quad 50 + 20 = 70 \\
\end{aligned}
}
$$