3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 307 · 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. 1.546 + 285 =
2. 2.879 − 186 =
3. 3.451 + 227 =
4. 4.700 − 171 =
5. 5.677 − 397 =
6. 6.968 − 785 =
7. 7.350 + 546 =
8. 8.626 + 192 =
9. 9.521 − 324 =
10. 10.240 + 489 =
11. 11.253 + 286 =
12. 12.238 + 682 =
13. 13.864 − 156 =
14. 14.724 − 525 =
15. 15.632 − 482 =
16. 16.174 + 549 =
17. 17.623 + 374 =
18. 18.153 + 205 =
19. 19.586 − 398 =
20. 20.304 + 463 =
21. 21.391 + 127 =
22. 22.288 + 268 =
23. 23.834 − 517 =
24. 24.916 − 239 =
25. 25.502 + 455 =
26. 26.618 − 146 =
27. 27.413 − 165 =
28. 28.859 − 297 =
29. 29.553 + 583 =
30. 30.484 + 645 =
31. 31.727 + 687 =
32. 32.958 − 357 =
33. 33.357 + 241 =
34. 34.672 + 251 =
35. 35.982 − 723 =
36. 36.484 − 363 =
37. 37.190 + 441 =
38. 38.780 + 409 =
39. 39.320 + 425 =
40. 40.779 + 123 =

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