Adding and Subtracting Within 1,000: Grade 3 Math Worksheet Answer Key – PDF Download

Grade 3 Add Worksheet Answer Key: problems 1–5

Problem 1: Adding with blocks

Add each place. Ones: \(3 + 6 = 9\). Tens: \(20 + 50 = 70\). Hundreds: \(100 + 200 = 300\).

\(123 + 256 = 379\). Answer: 379

Problem 2: Adding with regrouping ones

1. Ones: \(7 + 5 = 12\). Write 2 and regroup 1 ten.
2. Tens: \(4 + 3 + 1 = 8\).
3. Hundreds: \(2 + 1 = 3\).

\(247 + 135 = 382\). Answer: 382

Problem 3: Adding with regrouping tens

1. Ones: \(2 + 1 = 3\).
2. Tens: \(6 + 8 = 14\). Write 4 and regroup 1 hundred.
3. Hundreds: \(3 + 2 + 1 = 6\).

\(362 + 281 = 643\). Answer: 643

Problem 4: Regrouping twice

1. Ones: \(8 + 6 = 14\). Write 4 and regroup 1 ten.
2. Tens: \(7 + 5 + 1 = 13\). Write 3 and regroup 1 hundred.
3. Hundreds: \(4 + 2 + 1 = 7\).

\(478 + 256 = 734\). Answer: 734

Problem 5: Adding a two-digit number

1. Ones: \(7 + 6 = 13\). Write 3 and regroup 1 ten.
2. Tens: \(8 + 4 + 1 = 13\). Write 3 and regroup 1 hundred.
3. Hundreds: \(5 + 0 + 1 = 6\).

\(587 + 46 = 633\). Answer: 633

Grade 3 Add Worksheet Answer Key: problems 6–10

Problem 6: Subtracting without regrouping

1. Ones: \(6 – 3 = 3\).
2. Tens: \(5 – 2 = 3\).
3. Hundreds: \(7 – 4 = 3\).

\(756 – 423 = 333\). Answer: 333

Problem 7: Subtracting from blocks

Write \(342 – 118\).

1. Ones: not enough ones to subtract 8, so regroup. Now there are 12 ones.
2. Ones: \(12 – 8 = 4\).
3. Tens: \(3 – 1 = 2\).
4. Hundreds: \(3 – 1 = 2\).

\(342 – 118 = 224\). Answer: 224

Problem 8: Regrouping tens

1. Ones: \(4 – 2 = 2\).
2. Tens: not enough tens to subtract 8, so regroup. Now there are 13 tens.
3. Tens: \(13 – 8 = 5\).
4. Hundreds: \(4 – 1 = 3\).

\(534 – 182 = 352\). Answer: 352

Problem 9: Regrouping ones

1. Ones: not enough ones to subtract 8, so regroup. Now there are 15 ones.
2. Ones: \(15 – 8 = 7\).
3. Tens: not enough tens to subtract 4, so regroup. Now there are 11 tens.
4. Tens: \(11 – 4 = 7\).
5. Hundreds: \(6 – 3 = 3\).

\(725 – 348 = 377\). Answer: 377

Problem 10: Subtracting across a zero

1. Ones: not enough ones to subtract 7, so regroup. Now there are 10 ones.
2. Ones: \(10 – 7 = 3\).
3. Tens: \(9 – 5 = 4\).
4. Hundreds: \(5 – 2 = 3\).

\(600 – 257 = 343\). Answer: 343

Grade 3 Add Worksheet Answer Key: problems 11–15

Problem 11: Adding on a number line

\(285 + 100 = 385\), then \(385 + 40 = 425\).

Answer: 425

Problem 12: Subtracting on a number line

\(710 – 200 = 510\), then \(510 – 50 = 460\).

Answer: 460

Problem 13: Using a friendly number

398 is 2 less than 400. Add \(400 + 247 = 647\). Then take away the extra 2: \(647 – 2 = 645\).

Answer: 645

Problem 14: Subtracting a number close to 200

199 is 1 less than 200. Subtract \(465 – 200 = 265\). Subtracting 1 too many means add 1 back: \(265 + 1 = 266\).

Answer: 266

Problem 15: Finding a missing addend

Subtract: \(600 – 328 = 272\). Check: \(328 + 272 = 600\).

Answer: 272

Grade 3 Add Worksheet Answer Key: problems 16–20

Problem 16: Finding a missing start number

The start number is the difference plus the number taken away: \(417 + 245 = 662\). Check: \(662 – 245 = 417\).

Answer: 662

Problem 17: Estimate, then solve

Estimate: round 489 to 500 and 312 to 300. \(500 + 300 = 800\).

1. Ones: \(9 + 2 = 11\). Write 1 and regroup 1 ten.
2. Tens: \(8 + 1 + 1 = 10\). Write 0 and regroup 1 hundred.
3. Hundreds: \(4 + 3 + 1 = 8\).

Exact sum: \(489 + 312 = 801\), which is close to the estimate of 800.

Answer: estimate 800, exact 801

Problem 18: Checking with the inverse

Add the difference and the number taken away: \(445 + 258 = 703\). The sum matches the start number.

Answer: Yes, Maya is correct.

Problem 19: Comparing sums

\(468 + 275 = 743\) and \(512 + 189 = 701\). The first sum is greater. \(743 – 701 = 42\).

Answer: 468 + 275 is greater, by 42

Problem 20: Bake sale cookies

Add the two days: \(267 + 358\).

1. Ones: \(7 + 8 = 15\). Write 5 and regroup 1 ten.
2. Tens: \(6 + 5 + 1 = 12\). Write 2 and regroup 1 hundred.
3. Hundreds: \(2 + 3 + 1 = 6\).

Answer: 625 cookies

Grade 3 Add Worksheet Answer Key: problems 21–24

Problem 21: Library books

Subtract: \(805 – 379\).

1. Ones: not enough ones to subtract 9, so regroup. Now there are 15 ones.
2. Ones: \(15 – 9 = 6\).
3. Tens: \(9 – 7 = 2\).
4. Hundreds: \(7 – 3 = 4\).

Answer: 426 books

Problem 22: Farmers market sales

1. Maya sold \(156 + 238 = 394\) pieces of fruit.
2. Jamal sold \(394 – 87 = 307\) pieces.
3. Together: \(394 + 307 = 701\).

Answer: 701 pieces of fruit

Problem 23: Road trip miles

1. Miles driven: \(287 + 356 = 643\).
2. Miles left: \(900 – 643 = 257\).

Answer: 257 miles

Problem 24: Finding the mistake

Ones: \(4 + 9 = 13\), so 1 ten must be regrouped. Liam forgot to add that 1 ten. Tens: \(5 + 8 + 1 = 14\), so regroup 1 hundred. Hundreds: \(3 + 2 + 1 = 6\).

Correct sum: \(354 + 289 = 643\). Answer: 643; Liam forgot to add the regrouped ten

How to use this grade 3 add worksheet answer key

Read this grade 3 add worksheet answer key after trying each problem yourself, and redo any problem you missed.

See every chapter on the Grade 3 math page.