3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 560 · 40 questions

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

1. 1.445 + 634 =
2. 2.610 − 413 =
3. 3.507 − 177 =
4. 4.279 + 424 =
5. 5.678 − 298 =
6. 6.852 − 251 =
7. 7.505 − 216 =
8. 8.667 + 377 =
9. 9.375 + 391 =
10. 10.636 − 483 =
11. 11.572 − 405 =
12. 12.513 + 512 =
13. 13.548 + 645 =
14. 14.918 − 688 =
15. 15.325 + 384 =
16. 16.128 + 415 =
17. 17.847 − 115 =
18. 18.502 − 222 =
19. 19.765 − 228 =
20. 20.826 − 267 =
21. 21.702 + 579 =
22. 22.189 + 175 =
23. 23.492 + 229 =
24. 24.215 + 171 =
25. 25.454 + 456 =
26. 26.780 − 218 =
27. 27.502 − 187 =
28. 28.921 − 292 =
29. 29.651 − 426 =
30. 30.816 − 148 =
31. 31.143 + 226 =
32. 32.372 + 278 =
33. 33.617 + 323 =
34. 34.124 + 121 =
35. 35.702 − 236 =
36. 36.481 + 221 =
37. 37.876 − 479 =
38. 38.727 − 215 =
39. 39.715 − 571 =
40. 40.761 + 321 =

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