1. Estimation (Rounding and Compatible Numbers)
Grade 3
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3. Estimate sums by rounding
Estimate is to find an answer that is close to the exact answer.
In Rounding, the estimated answer can be greater than or less than the exact sum.
Addends are rounded up first and then the sum is calculated.
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4. Example Estimate 316 + 398 to the nearest hundreds.
Estimate each addend to the nearest hundred.
316 is rounded to 300
398 is rounded to 400
Add to find the estimated sum.
= 700
The estimated sum of is 700.
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5. Usefulness of Estimation
Estimation can be helpful to see if you have enough money to buy some items in the store.
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6. Estimating Sum using Place Value Model
Use Place Value model to show each addend rounded to the nearest (ten, hundred or thousand)
Combine model and find the estimated sum.
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7. Estimate sum by rounding to the nearest ten.
Add to the nearest ten.
Round 79 and 808 to the nearest ten.
79 is rounded to 80
808 is rounded to 810
Add
Answer- 890
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8. How can you estimate 246 + 89 in two different ways?
Round to the nearest hundred.
= 300
Round to the nearest ten.
= 340
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Exact number
To find exact number, no rounding off is required.
Add the numbers given in the problem.
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10. Estimate the sum to the nearest hundred. 220 + 390
Answer- 600
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11. Copyright © Ed2Net Learning, Inc.
Rose bought 23 hair pins in the month of June and 28 hair pins in the month of July. How many hair pins did she buy in all?
Exact answer is asked in the sum given above.
Thus, add 23 and 28.
The total hair pins she bought in the two months are 51
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12. Estimation and Exact : A Difference
The farmer bought 12 cows and 17 goats. About how many animals did he buy?
Exact
The farmer bought 12 cows and 17 goats. How many animals did he buy?
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Tell whether to estimate or find an exact number. Also find the answer to the problem.
Bon Park has 29 crows and 49 parrots. About how many birds are in the park?
Answer- Estimated answer is required 78
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Tim travels 43 minutes to and from the school each day. About how many minutes in all does Tim travel each day?
Answer- 80 minutes
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15. Find the Value of 8,569 + 569 rounded to the nearest hundred.
Answer- 7,200
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17. Try Assessment Questions Now.
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18. Show different ways to estimate the sum. 856 + 128
Answer-
Nearest ten - 990
Nearest hundred - 1,000
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19. 2. Estimate the Sum rounded to the nearest ten. 458 + 5,239
Answer- 5,700
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3. Rock has $50. He wants to buy a shirt for $15.50 and a pack of cards for $ Does he have enough money to buy the items?
Answer- Yes
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21. 4. Estimate ( to the nearest ten) and tell which is greater?
Answer- a
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is about 200. What is wrong with the sum, if the addends are rounded to nearest ten?
Answer rounded to the nearest ten is 170 and not 200
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6. Find the sum of exact and estimated value of 159 and 123 rounded to nearest ten.
Answer- 562
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24. 7. Use rounding to estimate each sum. Tell how you rounded.
Answer-
600, nearest hundred
140, nearest ten
700, nearest hundred
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8. A lion weighs 429 pounds and a tiger weighs 656 pounds. About how much do both weigh together?
Answer- 1,100 rounded to nearest hundred
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9. In a class voting 23 students vote for candidate A, while 29 students vote for Candidate B. What is the strength of the class?
Answer- 52 students
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27. 10. Add 2 + 8 + 7. Find the answer rounded to the nearest ten.
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Recap
Estimating sum by rounding
Usefulness of estimation
Estimation using Place value model
Exact Number
Estimation and Exact
Solved examples
Practice Problems
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Practice your worksheets to know more about Estimation.
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