3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 858 · 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. 1.256 + 311 =
2. 2.396 + 429 =
3. 3.343 + 672 =
4. 4.414 + 558 =
5. 5.708 + 383 =
6. 6.211 + 573 =
7. 7.774 + 558 =
8. 8.689 − 174 =
9. 9.866 − 198 =
10. 10.456 − 276 =
11. 11.711 − 519 =
12. 12.522 − 169 =
13. 13.356 + 661 =
14. 14.184 + 249 =
15. 15.499 + 556 =
16. 16.645 + 348 =
17. 17.584 − 206 =
18. 18.571 − 398 =
19. 19.690 + 234 =
20. 20.489 − 355 =
21. 21.896 − 527 =
22. 22.947 − 188 =
23. 23.749 + 551 =
24. 24.455 − 286 =
25. 25.518 + 503 =
26. 26.980 − 401 =
27. 27.744 − 151 =
28. 28.494 − 116 =
29. 29.145 + 137 =
30. 30.732 − 114 =
31. 31.513 + 594 =
32. 32.753 − 498 =
33. 33.521 + 264 =
34. 34.667 − 266 =
35. 35.823 − 243 =
36. 36.744 + 506 =
37. 37.655 − 403 =
38. 38.477 − 194 =
39. 39.987 − 367 =
40. 40.407 + 342 =

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