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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 71 · 40 questions
TalentJR

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.

NameDateTime takenScore ___ / 40
  1. 1.258 + 673 =
  2. 2.287 + 523 =
  3. 3.218 + 401 =
  4. 4.280 + 377 =
  5. 5.543 − 279 =
  6. 6.521 + 249 =
  7. 7.426 − 267 =
  8. 8.750 + 479 =
  9. 9.589 − 274 =
  10. 10.671 − 552 =
  11. 11.680 + 385 =
  12. 12.186 + 555 =
  13. 13.505 − 173 =
  14. 14.839 − 661 =
  15. 15.425 + 621 =
  16. 16.830 − 624 =
  17. 17.581 − 207 =
  18. 18.579 − 473 =
  19. 19.378 + 386 =
  20. 20.505 − 147 =
  21. 21.249 + 311 =
  22. 22.906 − 711 =
  23. 23.490 − 332 =
  24. 24.976 − 579 =
  25. 25.226 + 191 =
  26. 26.235 + 596 =
  27. 27.308 + 512 =
  28. 28.246 + 674 =
  29. 29.732 − 259 =
  30. 30.647 − 119 =
  31. 31.523 − 402 =
  32. 32.748 + 202 =
  33. 33.684 − 122 =
  34. 34.927 − 765 =
  35. 35.833 − 596 =
  36. 36.715 − 175 =
  37. 37.257 + 513 =
  38. 38.193 + 644 =
  39. 39.663 + 278 =
  40. 40.172 + 291 =

Answer key

  1. 931
  2. 810
  3. 619
  4. 657
  5. 264
  6. 770
  7. 159
  8. 1229
  9. 315
  10. 119
  11. 1065
  12. 741
  13. 332
  14. 178
  15. 1046
  16. 206
  17. 374
  18. 106
  19. 764
  20. 358
  21. 560
  22. 195
  23. 158
  24. 397
  25. 417
  26. 831
  27. 820
  28. 920
  29. 473
  30. 528
  31. 121
  32. 950
  33. 562
  34. 162
  35. 237
  36. 540
  37. 770
  38. 837
  39. 941
  40. 463

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