Let's solve each of the
3-digit addition problems step by step. We'll add the numbers column by column, starting from the right (ones place), carrying over when necessary.
---
1. 421 + 124
```
421
+124
-----
545
```
- 1 + 4 = 5 (ones)
- 2 + 2 = 4 (tens)
- 4 + 1 = 5 (hundreds)
✔ 545
---
2. 381 + 202
```
381
+202
-----
583
```
- 1 + 2 = 3
- 8 + 0 = 8
- 3 + 2 = 5
✔ 583
---
3. 643 + 321
```
643
+321
-----
964
```
- 3 + 1 = 4
- 4 + 2 = 6
- 6 + 3 = 9
✔ 964
---
4. 274 + 125
```
274
+125
-----
399
```
- 4 + 5 = 9
- 7 + 2 = 9
- 2 + 1 = 3
✔ 399
---
5. 392 + 103
```
392
+103
-----
495
```
- 2 + 3 = 5
- 9 + 0 = 9
- 3 + 1 = 4
✔ 495
---
6. 128 + 821
```
128
+821
-----
949
```
- 8 + 1 = 9
- 2 + 2 = 4
- 1 + 8 = 9
✔ 949
---
7. 346 + 352
```
346
+352
-----
698
```
- 6 + 2 = 8
- 4 + 5 = 9
- 3 + 3 = 6
✔ 698
---
8. 638 + 222
```
638
+222
-----
860
```
- 8 + 2 = 10 → write 0, carry 1
- 3 + 2 + 1 = 6
- 6 + 2 = 8
✔ 860
---
9. 821 + 177
```
821
+177
-----
998
```
- 1 + 7 = 8
- 2 + 7 = 9
- 8 + 1 = 9
✔ 998
---
10. 155 + 238
```
155
+238
-----
393
```
- 5 + 8 = 13 → write 3, carry 1
- 5 + 3 + 1 = 9
- 1 + 2 = 3
✔ 393
---
11. 447 + 227
```
447
+227
-----
674
```
- 7 + 7 = 14 → write 4, carry 1
- 4 + 2 + 1 = 7
- 4 + 2 = 6
✔ 674
---
12. 226 + 262
```
226
+262
-----
488
```
- 6 + 2 = 8
- 2 + 6 = 8
- 2 + 2 = 4
✔ 488
---
13. 724 + 137
```
724
+137
-----
861
```
- 4 + 7 = 11 → write 1, carry 1
- 2 + 3 + 1 = 6
- 7 + 1 = 8
✔ 861
---
14. 534 + 951
```
534
+951
-----
1485
```
- 4 + 1 = 5
- 3 + 5 = 8
- 5 + 9 = 14 → write 4, carry 1
- Carryover: 1 → so total is
1485
✔ 1485
---
15. 985 + 605
```
985
+605
-----
1590
```
- 5 + 5 = 10 → write 0, carry 1
- 8 + 0 + 1 = 9
- 9 + 6 = 15 → write 5, carry 1
- Carryover: 1 → so total is
1590
✔ 1590
---
16. 457 + 304
```
457
+304
-----
761
```
- 7 + 4 = 11 → write 1, carry 1
- 5 + 0 + 1 = 6
- 4 + 3 = 7
✔ 761
---
✔ Final Answers:
| Problem | Answer |
|--------|--------|
| 421 + 124 |
545 |
| 381 + 202 |
583 |
| 643 + 321 |
964 |
| 274 + 125 |
399 |
| 392 + 103 |
495 |
| 128 + 821 |
949 |
| 346 + 352 |
698 |
| 638 + 222 |
860 |
| 821 + 177 |
998 |
| 155 + 238 |
393 |
| 447 + 227 |
674 |
| 226 + 262 |
488 |
| 724 + 137 |
861 |
| 534 + 951 |
1485 |
| 985 + 605 |
1590 |
| 457 + 304 |
761 |
---
You can now fill in the boxes on the worksheet with these answers. Let me know if you'd like a printable version or explanation for any specific problem!
Parent Tip: Review the logic above to help your child master the concept of 3 addition digits worksheet.
