3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 810 · 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. 1.309 + 657 =
2. 2.856 − 125 =
3. 3.410 + 565 =
4. 4.974 − 658 =
5. 5.453 − 287 =
6. 6.591 + 683 =
7. 7.675 − 136 =
8. 8.757 − 575 =
9. 9.538 − 261 =
10. 10.788 − 424 =
11. 11.710 − 164 =
12. 12.977 − 564 =
13. 13.576 − 412 =
14. 14.750 − 281 =
15. 15.344 + 455 =
16. 16.648 − 497 =
17. 17.782 − 629 =
18. 18.443 − 199 =
19. 19.217 + 311 =
20. 20.725 − 146 =
21. 21.160 + 371 =
22. 22.762 + 544 =
23. 23.662 + 337 =
24. 24.141 + 301 =
25. 25.691 + 195 =
26. 26.519 − 129 =
27. 27.900 − 613 =
28. 28.153 + 346 =
29. 29.424 + 291 =
30. 30.515 − 331 =
31. 31.251 + 345 =
32. 32.340 + 597 =
33. 33.167 + 346 =
34. 34.936 − 272 =
35. 35.654 − 118 =
36. 36.947 − 221 =
37. 37.649 + 165 =
38. 38.136 + 417 =
39. 39.243 + 482 =
40. 40.390 + 248 =

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