3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 25 · 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. 1.124 + 561 =
2. 2.837 − 255 =
3. 3.618 + 141 =
4. 4.472 − 277 =
5. 5.812 − 645 =
6. 6.769 − 265 =
7. 7.554 + 538 =
8. 8.443 + 161 =
9. 9.476 − 158 =
10. 10.681 − 328 =
11. 11.149 + 511 =
12. 12.671 + 161 =
13. 13.642 + 382 =
14. 14.130 + 571 =
15. 15.341 + 254 =
16. 16.667 + 149 =
17. 17.643 − 382 =
18. 18.399 + 387 =
19. 19.437 − 196 =
20. 20.234 + 568 =
21. 21.582 − 158 =
22. 22.839 − 293 =
23. 23.618 − 209 =
24. 24.945 − 812 =
25. 25.670 + 592 =
26. 26.896 − 164 =
27. 27.369 + 452 =
28. 28.455 − 158 =
29. 29.651 + 489 =
30. 30.668 + 317 =
31. 31.308 + 426 =
32. 32.780 + 571 =
33. 33.687 − 344 =
34. 34.983 − 764 =
35. 35.510 + 143 =
36. 36.657 − 535 =
37. 37.647 − 537 =
38. 38.682 − 167 =
39. 39.798 − 483 =
40. 40.660 − 318 =

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