Math worksheet for rounding numbers and estimating sums.

Let's solve Activity 1 step by step.

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A. Round off each number based on its highest place value.

We round each number to the highest place value, which means:

- For a 3-digit number (like 578), the highest place is hundreds, so we round to the nearest hundred.
- For a 4-digit number (like 1093), the highest place is thousands, so we round to the nearest thousand.

---

#### 1. 578
- Highest place: hundreds
- Look at the tens digit: 7 ≥ 5 → round up
- 578 → 600

#### 2. 999
- Highest place: hundreds
- Tens digit: 9 ≥ 5 → round up
- 999 → 1000

#### 3. 805
- Highest place: hundreds
- Tens digit: 0 < 5 → round down
- 805 → 800

#### 4. 1093
- Highest place: thousands
- Hundreds digit: 0 < 5 → round down
- 1093 → 1000

#### 5. 4839
- Highest place: thousands
- Hundreds digit: 8 ≥ 5 → round up
- 4839 → 5000

---

✔ A Answers:
1. 600
2. 1000
3. 800
4. 1000
5. 5000

---

B. Estimate each sum. Type the rounded off values of the addends.

We will:
1. Round each addend to its highest place value.
2. Add the rounded numbers to estimate the sum.

---

#### 1. 459 + 402
- 459 → hundreds: 500 (since 459 → 500)
- 402 → hundreds: 400 (since 402 → 400)
- Estimated sum: 500 + 400 = 900

```
459 → 500
+ 402 → 400
---------
900
```

---

#### 2. 7384 + 2985
- 7384 → thousands: 7000 (hundreds digit = 3 < 5 → round down)
- 2985 → thousands: 3000 (hundreds digit = 9 ≥ 5 → round up)
- Estimated sum: 7000 + 3000 = 10,000

```
7384 → 7000
+2985 → 3000
----------
10000
```

---

#### 3. 8643 + 9234
- 8643 → thousands: 9000 (hundreds digit = 6 ≥ 5 → round up)
- 9234 → thousands: 9000 (hundreds digit = 2 < 5 → round down)
- Estimated sum: 9000 + 9000 = 18,000

```
8643 → 9000
+9234 → 9000
----------
18000
```

---

#### 4. 5901 + 8362
- 5901 → thousands: 6000 (hundreds digit = 9 ≥ 5 → round up)
- 8362 → thousands: 8000 (hundreds digit = 3 < 5 → round down)
- Estimated sum: 6000 + 8000 = 14,000

```
5901 → 6000
+8362 → 8000
----------
14000
```

---

#### 5. 784 + 278 + 329
- All are 3-digit numbers → round to hundreds
- 784 → 800 (tens digit = 8 ≥ 5 → round up)
- 278 → 300 (tens digit = 7 ≥ 5 → round up)
- 329 → 300 (tens digit = 2 < 5 → round down)
- Estimated sum: 800 + 300 + 300 = 1400

```
784 → 800
+278 → 300
+329 → 300
----------
1400
```

---

#### 6. 1851 + 3006 + 4532
- All are 4-digit numbers → round to thousands
- 1851 → 2000 (hundreds digit = 8 ≥ 5 → round up)
- 3006 → 3000 (hundreds digit = 0 < 5 → round down)
- 4532 → 5000 (hundreds digit = 5 → round up)
- Estimated sum: 2000 + 3000 + 5000 = 10,000

```
1851 → 2000
+3006 → 3000
+4532 → 5000
----------
10000
```

---

✔ Final Answers:

#### A. Round off each number:
1. 578 → 600
2. 999 → 1000
3. 805 → 800
4. 1093 → 1000
5. 4839 → 5000

---

#### B. Estimate each sum:

1.
```
459 → 500
+ 402 → 400
---------
900
```

2.
```
7384 → 7000
+2985 → 3000
----------
10000
```

3.
```
8643 → 9000
+9234 → 9000
----------
18000
```

4.
```
5901 → 6000
+8362 → 8000
----------
14000
```

5.
```
784 → 800
+278 → 300
+329 → 300
----------
1400
```

6.
```
1851 → 2000
+3006 → 3000
+4532 → 5000
----------
10000
```

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