3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 658 · 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. 1.423 + 156 =
2. 2.642 − 304 =
3. 3.123 + 487 =
4. 4.471 − 142 =
5. 5.678 − 451 =
6. 6.551 − 317 =
7. 7.488 − 141 =
8. 8.757 − 513 =
9. 9.638 − 121 =
10. 10.228 + 285 =
11. 11.656 + 441 =
12. 12.676 − 243 =
13. 13.803 − 441 =
14. 14.423 − 205 =
15. 15.650 − 369 =
16. 16.815 − 389 =
17. 17.596 − 378 =
18. 18.593 + 624 =
19. 19.770 − 568 =
20. 20.941 − 113 =
21. 21.374 + 243 =
22. 22.975 − 545 =
23. 23.930 − 182 =
24. 24.790 − 267 =
25. 25.522 − 276 =
26. 26.648 − 358 =
27. 27.682 + 626 =
28. 28.784 − 411 =
29. 29.550 + 187 =
30. 30.195 + 252 =
31. 31.450 − 219 =
32. 32.540 − 141 =
33. 33.903 − 284 =
34. 34.689 + 121 =
35. 35.585 − 171 =
36. 36.398 + 363 =
37. 37.657 − 543 =
38. 38.560 − 205 =
39. 39.709 − 118 =
40. 40.666 + 475 =

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