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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 512 · 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. 1.435 + 613 =
  2. 2.600 + 664 =
  3. 3.636 + 413 =
  4. 4.130 + 163 =
  5. 5.641 + 358 =
  6. 6.477 − 306 =
  7. 7.590 + 379 =
  8. 8.857 − 556 =
  9. 9.859 − 542 =
  10. 10.345 + 426 =
  11. 11.702 + 354 =
  12. 12.766 + 444 =
  13. 13.566 + 226 =
  14. 14.244 + 471 =
  15. 15.203 + 604 =
  16. 16.335 + 557 =
  17. 17.234 + 415 =
  18. 18.881 − 483 =
  19. 19.716 + 359 =
  20. 20.746 − 367 =
  21. 21.594 − 217 =
  22. 22.349 + 319 =
  23. 23.511 − 371 =
  24. 24.842 − 413 =
  25. 25.766 + 491 =
  26. 26.654 − 158 =
  27. 27.408 + 432 =
  28. 28.637 − 275 =
  29. 29.132 + 271 =
  30. 30.390 + 227 =
  31. 31.548 − 361 =
  32. 32.224 + 546 =
  33. 33.498 − 144 =
  34. 34.936 − 661 =
  35. 35.676 − 573 =
  36. 36.558 − 346 =
  37. 37.844 − 507 =
  38. 38.434 − 301 =
  39. 39.490 − 311 =
  40. 40.153 + 131 =

Answer key

  1. 1048
  2. 1264
  3. 1049
  4. 293
  5. 999
  6. 171
  7. 969
  8. 301
  9. 317
  10. 771
  11. 1056
  12. 1210
  13. 792
  14. 715
  15. 807
  16. 892
  17. 649
  18. 398
  19. 1075
  20. 379
  21. 377
  22. 668
  23. 140
  24. 429
  25. 1257
  26. 496
  27. 840
  28. 362
  29. 403
  30. 617
  31. 187
  32. 770
  33. 354
  34. 275
  35. 103
  36. 212
  37. 337
  38. 133
  39. 179
  40. 284

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