Math worksheet for estimating sums by rounding numbers, suitable for pre-algebra students.
A math worksheet titled "Make an Estimate" from Frank Schaffer Publications, Inc., designed to teach rounding numbers and mental addition to estimate sums, featuring examples and problems labeled A through E with decimal numbers.
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Show Answer Key & Explanations
Step-by-step solution for: Decimals by Tina Sparks ONeal - Issuu
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Show Answer Key & Explanations
Step-by-step solution for: Decimals by Tina Sparks ONeal - Issuu
Let's solve this step-by-step. The task is to estimate the sum of each addition problem by rounding the numbers first, then adding mentally.
We'll go through each section (A through E), rounding appropriately and estimating the sums.
---
- Round each number to a place that makes sense (usually nearest whole number or nearest tenth depending on size).
- Add the rounded numbers mentally.
- Write the estimated sum.
---
## ✔ Section A
2.04 + 5.75
- Round 2.04 → 2
- Round 5.75 → 6
- Estimate: 2 + 6 = 8
✔ Estimated sum: 8
---
6.014 + 3.275
- Round 6.014 → 6
- Round 3.275 → 3
- Estimate: 6 + 3 = 9
✔ Estimated sum: 9
---
10.33 + 17.4
- Round 10.33 → 10
- Round 17.4 → 17
- Estimate: 10 + 17 = 27
✔ Estimated sum: 27
---
3.49 + 15.52
- Round 3.49 → 3
- Round 15.52 → 16
- Estimate: 3 + 16 = 19
✔ Estimated sum: 19
---
## ✔ Section B
87.43 + 80.40
- Round 87.43 → 87
- Round 80.40 → 80
- Estimate: 87 + 80 = 167
✔ Estimated sum: 167
---
1.28 + 9.40
- Round 1.28 → 1
- Round 9.40 → 9
- Estimate: 1 + 9 = 10
✔ Estimated sum: 10
---
61.29 + 59.24
- Round 61.29 → 61
- Round 59.24 → 59
- Estimate: 61 + 59 = 120
✔ Estimated sum: 120
---
22.14 + 95.52
- Round 22.14 → 22
- Round 95.52 → 96
- Estimate: 22 + 96 = 118
✔ Estimated sum: 118
---
2.4 + 39.6
- Round 2.4 → 2
- Round 39.6 → 40
- Estimate: 2 + 40 = 42
✔ Estimated sum: 42
---
## ✔ Section C
5.37 + 3.79
- Round 5.37 → 5
- Round 3.79 → 4
- Estimate: 5 + 4 = 9
✔ Estimated sum: 9
---
29.34 + 34.56
- Round 29.34 → 29
- Round 34.56 → 35
- Estimate: 29 + 35 = 64
✔ Estimated sum: 64
---
70.16 + 45.42
- Round 70.16 → 70
- Round 45.42 → 45
- Estimate: 70 + 45 = 115
✔ Estimated sum: 115
---
256.11 + 29.93
- Round 256.11 → 256
- Round 29.93 → 30
- Estimate: 256 + 30 = 286
✔ Estimated sum: 286
---
49.99 + 34.56
- Round 49.99 → 50
- Round 34.56 → 35
- Estimate: 50 + 35 = 85
✔ Estimated sum: 85
---
## ✔ Section D
24.92 + 76.38 + 67.21
- Round:
- 24.92 → 25
- 76.38 → 76
- 67.21 → 67
- Estimate: 25 + 76 = 101, then 101 + 67 = 168
✔ Estimated sum: 168
---
74.89 + 27.36 + 56.03
- Round:
- 74.89 → 75
- 27.36 → 27
- 56.03 → 56
- Estimate: 75 + 27 = 102, then 102 + 56 = 158
✔ Estimated sum: 158
---
19.55 + 4.46 + 20.26
- Round:
- 19.55 → 20
- 4.46 → 4
- 20.26 → 20
- Estimate: 20 + 4 = 24, then 24 + 20 = 44
✔ Estimated sum: 44
---
124.95 + 59.50 + 100.40
- Round:
- 124.95 → 125
- 59.50 → 60
- 100.40 → 100
- Estimate: 125 + 60 = 185, then 185 + 100 = 285
✔ Estimated sum: 285
---
9.95 + 41.45 + 60.88
- Round:
- 9.95 → 10
- 41.45 → 41
- 60.88 → 61
- Estimate: 10 + 41 = 51, then 51 + 61 = 112
✔ Estimated sum: 112
---
## ✔ Section E
21.07 + 39.54 + 60.24
- Round:
- 21.07 → 21
- 39.54 → 40
- 60.24 → 60
- Estimate: 21 + 40 = 61, then 61 + 60 = 121
✔ Estimated sum: 121
---
70.88 + 12.45 + 3.98
- Round:
- 70.88 → 71
- 12.45 → 12
- 3.98 → 4
- Estimate: 71 + 12 = 83, then 83 + 4 = 87
✔ Estimated sum: 87
---
26.97 + 39.51 + 59.94
- Round:
- 26.97 → 27
- 39.51 → 40
- 59.94 → 60
- Estimate: 27 + 40 = 67, then 67 + 60 = 127
✔ Estimated sum: 127
---
13.06 + 26.91 + 5.27
- Round:
- 13.06 → 13
- 26.91 → 27
- 5.27 → 5
- Estimate: 13 + 27 = 40, then 40 + 5 = 45
✔ Estimated sum: 45
---
434.15 + 202.01 + 46.82
- Round:
- 434.15 → 434
- 202.01 → 202
- 46.82 → 47
- Estimate: 434 + 202 = 636, then 636 + 47 = 683
✔ Estimated sum: 683
---
## ✔ Final Answers Summary:
1. 8
2. 9
3. 27
4. 19
1. 167
2. 10
3. 120
4. 118
5. 42
1. 9
2. 64
3. 115
4. 286
5. 85
1. 168
2. 158
3. 44
4. 285
5. 112
1. 121
2. 87
3. 127
4. 45
5. 683
---
- We rounded each number to the nearest whole number or nearest ten/tenth based on the context.
- Then we added the rounded values mentally.
- This gives us a close approximation of the actual sum, which helps in checking if an exact answer is reasonable.
Let me know if you'd like the actual sums for comparison!
We'll go through each section (A through E), rounding appropriately and estimating the sums.
---
🔷 Guidelines:
- Round each number to a place that makes sense (usually nearest whole number or nearest tenth depending on size).
- Add the rounded numbers mentally.
- Write the estimated sum.
---
## ✔ Section A
1.
2.04 + 5.75
- Round 2.04 → 2
- Round 5.75 → 6
- Estimate: 2 + 6 = 8
✔ Estimated sum: 8
---
2.
6.014 + 3.275
- Round 6.014 → 6
- Round 3.275 → 3
- Estimate: 6 + 3 = 9
✔ Estimated sum: 9
---
3.
10.33 + 17.4
- Round 10.33 → 10
- Round 17.4 → 17
- Estimate: 10 + 17 = 27
✔ Estimated sum: 27
---
4.
3.49 + 15.52
- Round 3.49 → 3
- Round 15.52 → 16
- Estimate: 3 + 16 = 19
✔ Estimated sum: 19
---
## ✔ Section B
1.
87.43 + 80.40
- Round 87.43 → 87
- Round 80.40 → 80
- Estimate: 87 + 80 = 167
✔ Estimated sum: 167
---
2.
1.28 + 9.40
- Round 1.28 → 1
- Round 9.40 → 9
- Estimate: 1 + 9 = 10
✔ Estimated sum: 10
---
3.
61.29 + 59.24
- Round 61.29 → 61
- Round 59.24 → 59
- Estimate: 61 + 59 = 120
✔ Estimated sum: 120
---
4.
22.14 + 95.52
- Round 22.14 → 22
- Round 95.52 → 96
- Estimate: 22 + 96 = 118
✔ Estimated sum: 118
---
5.
2.4 + 39.6
- Round 2.4 → 2
- Round 39.6 → 40
- Estimate: 2 + 40 = 42
✔ Estimated sum: 42
---
## ✔ Section C
1.
5.37 + 3.79
- Round 5.37 → 5
- Round 3.79 → 4
- Estimate: 5 + 4 = 9
✔ Estimated sum: 9
---
2.
29.34 + 34.56
- Round 29.34 → 29
- Round 34.56 → 35
- Estimate: 29 + 35 = 64
✔ Estimated sum: 64
---
3.
70.16 + 45.42
- Round 70.16 → 70
- Round 45.42 → 45
- Estimate: 70 + 45 = 115
✔ Estimated sum: 115
---
4.
256.11 + 29.93
- Round 256.11 → 256
- Round 29.93 → 30
- Estimate: 256 + 30 = 286
✔ Estimated sum: 286
---
5.
49.99 + 34.56
- Round 49.99 → 50
- Round 34.56 → 35
- Estimate: 50 + 35 = 85
✔ Estimated sum: 85
---
## ✔ Section D
1.
24.92 + 76.38 + 67.21
- Round:
- 24.92 → 25
- 76.38 → 76
- 67.21 → 67
- Estimate: 25 + 76 = 101, then 101 + 67 = 168
✔ Estimated sum: 168
---
2.
74.89 + 27.36 + 56.03
- Round:
- 74.89 → 75
- 27.36 → 27
- 56.03 → 56
- Estimate: 75 + 27 = 102, then 102 + 56 = 158
✔ Estimated sum: 158
---
3.
19.55 + 4.46 + 20.26
- Round:
- 19.55 → 20
- 4.46 → 4
- 20.26 → 20
- Estimate: 20 + 4 = 24, then 24 + 20 = 44
✔ Estimated sum: 44
---
4.
124.95 + 59.50 + 100.40
- Round:
- 124.95 → 125
- 59.50 → 60
- 100.40 → 100
- Estimate: 125 + 60 = 185, then 185 + 100 = 285
✔ Estimated sum: 285
---
5.
9.95 + 41.45 + 60.88
- Round:
- 9.95 → 10
- 41.45 → 41
- 60.88 → 61
- Estimate: 10 + 41 = 51, then 51 + 61 = 112
✔ Estimated sum: 112
---
## ✔ Section E
1.
21.07 + 39.54 + 60.24
- Round:
- 21.07 → 21
- 39.54 → 40
- 60.24 → 60
- Estimate: 21 + 40 = 61, then 61 + 60 = 121
✔ Estimated sum: 121
---
2.
70.88 + 12.45 + 3.98
- Round:
- 70.88 → 71
- 12.45 → 12
- 3.98 → 4
- Estimate: 71 + 12 = 83, then 83 + 4 = 87
✔ Estimated sum: 87
---
3.
26.97 + 39.51 + 59.94
- Round:
- 26.97 → 27
- 39.51 → 40
- 59.94 → 60
- Estimate: 27 + 40 = 67, then 67 + 60 = 127
✔ Estimated sum: 127
---
4.
13.06 + 26.91 + 5.27
- Round:
- 13.06 → 13
- 26.91 → 27
- 5.27 → 5
- Estimate: 13 + 27 = 40, then 40 + 5 = 45
✔ Estimated sum: 45
---
5.
434.15 + 202.01 + 46.82
- Round:
- 434.15 → 434
- 202.01 → 202
- 46.82 → 47
- Estimate: 434 + 202 = 636, then 636 + 47 = 683
✔ Estimated sum: 683
---
## ✔ Final Answers Summary:
A.
1. 8
2. 9
3. 27
4. 19
B.
1. 167
2. 10
3. 120
4. 118
5. 42
C.
1. 9
2. 64
3. 115
4. 286
5. 85
D.
1. 168
2. 158
3. 44
4. 285
5. 112
E.
1. 121
2. 87
3. 127
4. 45
5. 683
---
📌 Explanation:
- We rounded each number to the nearest whole number or nearest ten/tenth based on the context.
- Then we added the rounded values mentally.
- This gives us a close approximation of the actual sum, which helps in checking if an exact answer is reasonable.
Let me know if you'd like the actual sums for comparison!
Parent Tip: Review the logic above to help your child master the concept of frank schaffer publications worksheet answers.
