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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 726 · 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. 1.143 + 681 =
  2. 2.493 − 151 =
  3. 3.646 − 436 =
  4. 4.480 − 197 =
  5. 5.691 + 337 =
  6. 6.438 + 482 =
  7. 7.213 + 526 =
  8. 8.281 + 316 =
  9. 9.635 + 212 =
  10. 10.914 − 174 =
  11. 11.728 + 167 =
  12. 12.421 − 172 =
  13. 13.356 + 175 =
  14. 14.323 + 436 =
  15. 15.903 − 524 =
  16. 16.541 − 112 =
  17. 17.487 − 226 =
  18. 18.721 − 507 =
  19. 19.617 + 322 =
  20. 20.407 + 577 =
  21. 21.131 + 143 =
  22. 22.717 − 187 =
  23. 23.683 + 614 =
  24. 24.497 − 202 =
  25. 25.442 + 151 =
  26. 26.786 + 576 =
  27. 27.813 − 401 =
  28. 28.525 + 447 =
  29. 29.663 + 334 =
  30. 30.843 − 467 =
  31. 31.584 + 601 =
  32. 32.679 − 431 =
  33. 33.820 − 344 =
  34. 34.352 + 361 =
  35. 35.891 − 594 =
  36. 36.552 − 245 =
  37. 37.174 + 609 =
  38. 38.505 − 219 =
  39. 39.182 + 671 =
  40. 40.256 + 304 =

Answer key

  1. 824
  2. 342
  3. 210
  4. 283
  5. 1028
  6. 920
  7. 739
  8. 597
  9. 847
  10. 740
  11. 895
  12. 249
  13. 531
  14. 759
  15. 379
  16. 429
  17. 261
  18. 214
  19. 939
  20. 984
  21. 274
  22. 530
  23. 1297
  24. 295
  25. 593
  26. 1362
  27. 412
  28. 972
  29. 997
  30. 376
  31. 1185
  32. 248
  33. 476
  34. 713
  35. 297
  36. 307
  37. 783
  38. 286
  39. 853
  40. 560

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