This grade 3 rounding worksheet answer key solves all 24 problems of the rounding to the nearest 10 and 100 worksheet step by step.
Every answer shows the digit you look at and why the number rounds up or down. Use the steps to check your work, then fix any mistakes and try the problem again.
Grade 3 Rounding Worksheet Answer Key: problems 1–5
Problem 1: Round to the nearest 10, ones digit small
The ones digit is 3, which is less than 5. Keep the tens digit and write 0 in the ones place.
\(23\) rounds to \(20\).
Problem 2: Round to the nearest 10, ones digit large
The ones digit is 8, which is 5 or more. Add 1 to the tens digit: 5 + 1 = 6.
\(58\) rounds to \(60\).
Problem 3: Four numbers to the nearest 10
- \(71\) rounds to \(70\) (ones digit 1).
- \(76\) rounds to \(80\) (ones digit 6).
- \(74\) rounds to \(70\) (ones digit 4).
- \(79\) rounds to \(80\) (ones digit 9).
Problem 4: Halfway numbers
- \(45\) is halfway, so it rounds up to \(50\).
- \(85\) is halfway, so it rounds up to \(90\).
- \(135\) is halfway, so it rounds up to \(140\).
Problem 5: Which ten is closer?
The point is before the halfway mark 85, so it is closer to 80. Check: 83 − 80 = 3 and 90 − 83 = 7.
The closer ten is \(80\).
Grade 3 Rounding Worksheet Answer Key: problems 6–10
Problem 6: Three-digit numbers to the nearest 10
- \(142\) rounds to \(140\) (ones digit 2).
- \(367\) rounds to \(370\) (ones digit 7).
- \(505\) rounds to \(510\) (ones digit 5).
- \(996\) rounds to \(1,000\) (ones digit 6).
Problem 7: Round to the nearest 100
- \(312\) rounds to \(300\) (tens digit 1).
- \(689\) rounds to \(700\) (tens digit 8).
- \(450\) rounds to \(500\) (tens digit 5).
- \(950\) rounds to \(1,000\) (tens digit 5).
Problem 8: Hundreds on a number line
The halfway mark is 650. Since 640 is before 650, it is closer to 600.
\(640\) rounds to \(600\).
Problem 9: Rounding 99 to the nearest 10
The ones digit is 9, so round up. The tens digit 9 plus 1 equals 10 tens, which is 100.
\(99\) rounds to \(100\).
Problem 10: Complete the rounding table
| Number | Nearest 10 | Nearest 100 |
|---|---|---|
| 276 | 280 | 300 |
| 543 | 540 | 500 |
| 805 | 810 | 800 |
| 99 | 100 | 100 |
Grade 3 Rounding Worksheet Answer Key: problems 11–15
Problem 11: Numbers that round to 40
Round each number: 31 → 30, 34 → 30, 35 → 40, 38 → 40, 41 → 40.
The numbers that round to 40 are 35, 38, and 41.
Problem 12: Smallest and greatest
The numbers must be at least 55 (halfway rounds up) and less than 65 (65 rounds up to 70).
Smallest: 55. Greatest: 64.
Problem 13: Range for 300
The halfway points are 250 and 350. The number 250 rounds up to 300. The number 350 rounds up to 400, so it is too big.
Smallest: 250. Greatest: 349.
Problem 14: Find the mistake: hundreds
Look at the tens digit. It is 6, which is 5 or more, so the hundreds digit goes up by 1.
Liam is not right. \(465\) rounds to \(500\).
Problem 15: Two different roundings
To the nearest 10, the ones digit 8 sends the 4 tens up to 5 tens, so 248 rounds to 250.
To the nearest 100, the tens digit 4 is less than 5, so the hundreds digit 2 stays. 248 rounds to 200.
Each place looks at a different digit, so the results can differ.
Grade 3 Rounding Worksheet Answer Key: problems 16–20
Problem 16: Round and compare
548 rounds to 500 (tens digit 4). 652 rounds to 700 (tens digit 5).
\(500 < 700\). The answer is \(500 < 700\).
Problem 17: Estimate a sum
38 rounds to 40. 47 rounds to 50.
\(40 + 50 = 90\).
The estimate is 90. (The exact sum, 85, is close.)
Problem 18: Estimate a difference
683 rounds to 700. 216 rounds to 200.
\(700 – 200 = 500\).
The estimate is 500. (The exact answer, 467, is close.)
Problem 19: Road trip miles
Nearest 10: the ones digit 7 rounds up, so 237 → 240.
Nearest 100: the tens digit 3 is small, so 237 → 200.
About 240 miles to the nearest 10 and about 200 miles to the nearest 100.
Problem 20: Bake sale estimate
$153 rounds to $200 and $248 rounds to $200. Estimate: $200 + $200 = $400.
Exact: $153 + $248 = $401.
The estimate is $400 and the exact total is $401. The estimate is close, so the answer is reasonable.
Grade 3 Rounding Worksheet Answer Key: problems 21–24
Problem 21: Can drive
482 rounds to 500. 317 rounds to 300.
500 − 300 = 200.
Jamal’s class collected about 200 more cans. (Exact: 482 − 317 = 165.)
Problem 22: Game attendance
The halfway points around 600 are 550 and 650. The number 550 rounds up to 600, but 650 rounds up to 700.
Least: 550 fans. Greatest: 649 fans.
Problem 23: Pages read
38 → 40, 47 → 50, 52 → 50.
40 + 50 + 50 = 140.
Sofia read about 140 pages. (Exact: 137 pages.)
Problem 24: Is Ethan right?
The halfway point between 300 and 400 is 350. The number 351 is just past 350, so it is closer to 400. The tens digit 5 also tells us to round up.
Yes, Ethan is right: 351 rounds to 400.
How to use this grade 3 rounding worksheet answer key
Read this grade 3 rounding worksheet answer key after trying each problem yourself, and redo any problem you missed.
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Grade 3 Rounding to the Nearest 10 and 100 worksheet answer key
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