25) addition, adding 3-digit numbers Math Worksheets, Math ... - Free Printable

Let’s solve each addition problem step by step. We’ll add the numbers column by column, starting from the right (ones place), then tens, then hundreds. If a column adds up to 10 or more, we carry over to the next column.

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First row:

1. 421 + 131
Ones: 1 + 1 = 2
Tens: 2 + 3 = 5
Hundreds: 4 + 1 = 5
→ 552

2. 630 + 385
Ones: 0 + 5 = 5
Tens: 3 + 8 = 11 → write 1, carry 1
Hundreds: 6 + 3 + 1 (carry) = 10 → write 0, carry 1 → but no thousands? Wait — actually, 6+3=9, plus 1 carry = 10 → so it’s 1015? Let me check again:
Actually:
630
+385
----
0+5=5
3+8=11 → write 1, carry 1
6+3=9, plus 1 = 10 → so 1015? That can’t be right for 3-digit + 3-digit? Wait — 630 + 385 is indeed 1015. Yes, that’s correct.
→ 1015

Wait — let me double-check with another method:
630 + 300 = 930; 930 + 85 = 1015. Correct.

3. 321 + 295
Ones: 1 + 5 = 6
Tens: 2 + 9 = 11 → write 1, carry 1
Hundreds: 3 + 2 + 1 = 6
→ 616

4. 879 + 414
Ones: 9 + 4 = 13 → write 3, carry 1
Tens: 7 + 1 + 1 = 9
Hundreds: 8 + 4 = 12 → write 2, carry 1 → so 1293?
Let’s do it:
879
+414
----
9+4=13 → 3, carry 1
7+1=8, +1=9
8+4=12 → so 1293
→ 1293

5. 771 + 571
Ones: 1 + 1 = 2
Tens: 7 + 7 = 14 → write 4, carry 1
Hundreds: 7 + 5 + 1 = 13 → write 3, carry 1 → so 1342
→ 1342

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Second row:

6. 525 + 924
Ones: 5 + 4 = 9
Tens: 2 + 2 = 4
Hundreds: 5 + 9 = 14 → write 4, carry 1 → so 1449
→ 1449

7. 258 + 189
Ones: 8 + 9 = 17 → write 7, carry 1
Tens: 5 + 8 + 1 = 14 → write 4, carry 1
Hundreds: 2 + 1 + 1 = 4
→ 447

8. 442 + 440
Ones: 2 + 0 = 2
Tens: 4 + 4 = 8
Hundreds: 4 + 4 = 8
→ 882

9. 666 + 931
Ones: 6 + 1 = 7
Tens: 6 + 3 = 9
Hundreds: 6 + 9 = 15 → write 5, carry 1 → so 1597
→ 1597

10. 184 + 267
Ones: 4 + 7 = 11 → write 1, carry 1
Tens: 8 + 6 + 1 = 15 → write 5, carry 1
Hundreds: 1 + 2 + 1 = 4
→ 451

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Third row:

11. 918 + 429
Ones: 8 + 9 = 17 → write 7, carry 1
Tens: 1 + 2 + 1 = 4
Hundreds: 9 + 4 = 13 → write 3, carry 1 → so 1347
→ 1347

12. 640 + 900
Ones: 0 + 0 = 0
Tens: 4 + 0 = 4
Hundreds: 6 + 9 = 15 → write 5, carry 1 → so 1540
→ 1540

13. 842 + 367
Ones: 2 + 7 = 9
Tens: 4 + 6 = 10 → write 0, carry 1
Hundreds: 8 + 3 + 1 = 12 → write 2, carry 1 → so 1209
→ 1209

14. 811 + 908
Ones: 1 + 8 = 9
Tens: 1 + 0 = 1
Hundreds: 8 + 9 = 17 → write 7, carry 1 → so 1719
→ 1719

15. 258 + 491
Ones: 8 + 1 = 9
Tens: 5 + 9 = 14 → write 4, carry 1
Hundreds: 2 + 4 + 1 = 7
→ 749

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Fourth row:

16. 326 + 563
Ones: 6 + 3 = 9
Tens: 2 + 6 = 8
Hundreds: 3 + 5 = 8
→ 889

17. 349 + 671
Ones: 9 + 1 = 10 → write 0, carry 1
Tens: 4 + 7 + 1 = 12 → write 2, carry 1
Hundreds: 3 + 6 + 1 = 10 → write 0, carry 1 → so 1020
→ 1020

18. 732 + 891
Ones: 2 + 1 = 3
Tens: 3 + 9 = 12 → write 2, carry 1
Hundreds: 7 + 8 + 1 = 16 → write 6, carry 1 → so 1623
→ 1623

19. 533 + 334
Ones: 3 + 4 = 7
Tens: 3 + 3 = 6
Hundreds: 5 + 3 = 8
→ 867

20. 690 + 357
Ones: 0 + 7 = 7
Tens: 9 + 5 = 14 → write 4, carry 1
Hundreds: 6 + 3 + 1 = 10 → write 0, carry 1 → so 1047
→ 1047

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Fifth row:

21. 454 + 257
Ones: 4 + 7 = 11 → write 1, carry 1
Tens: 5 + 5 + 1 = 11 → write 1, carry 1
Hundreds: 4 + 2 + 1 = 7
→ 711

22. 127 + 892
Ones: 7 + 2 = 9
Tens: 2 + 9 = 11 → write 1, carry 1
Hundreds: 1 + 8 + 1 = 10 → write 0, carry 1 → so 1019
→ 1019

23. 985 + 866
Ones: 5 + 6 = 11 → write 1, carry 1
Tens: 8 + 6 + 1 = 15 → write 5, carry 1
Hundreds: 9 + 8 + 1 = 18 → write 8, carry 1 → so 1851
→ 1851

24. 671 + 699
Ones: 1 + 9 = 10 → write 0, carry 1
Tens: 7 + 9 + 1 = 17 → write 7, carry 1
Hundreds: 6 + 6 + 1 = 13 → write 3, carry 1 → so 1370
→ 1370

25. 657 + 530
Ones: 7 + 0 = 7
Tens: 5 + 3 = 8
Hundreds: 6 + 5 = 11 → write 1, carry 1 → so 1187
→ 1187

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Now, let’s list all answers in order:

Row 1: 552, 1015, 616, 1293, 1342
Row 2: 1449, 447, 882, 1597, 451
Row 3: 1347, 1540, 1209, 1719, 749
Row 4: 889, 1020, 1623, 867, 1047
Row 5: 711, 1019, 1851, 1370, 1187

I’ll now verify a few random ones to make sure I didn’t make a mistake.

Check #7: 258 + 189
258 + 180 = 438; 438 + 9 = 447 → correct.

Check #17: 349 + 671
349 + 600 = 949; 949 + 71 = 1020 → correct.

Check #23: 985 + 866
985 + 800 = 1785; 1785 + 66 = 1851 → correct.

All seem good.

Final Answer:
552, 1015, 616, 1293, 1342, 1449, 447, 882, 1597, 451, 1347, 1540, 1209, 1719, 749, 889, 1020, 1623, 867, 1047, 711, 1019, 1851, 1370, 1187