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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 904 · 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. 1.403 + 572 =
  2. 2.886 − 557 =
  3. 3.631 + 269 =
  4. 4.734 + 611 =
  5. 5.715 − 469 =
  6. 6.647 + 687 =
  7. 7.394 + 595 =
  8. 8.691 + 568 =
  9. 9.288 + 168 =
  10. 10.871 − 148 =
  11. 11.137 + 168 =
  12. 12.663 + 188 =
  13. 13.606 + 573 =
  14. 14.529 + 159 =
  15. 15.138 + 635 =
  16. 16.189 + 653 =
  17. 17.602 − 121 =
  18. 18.388 + 163 =
  19. 19.310 + 192 =
  20. 20.806 − 438 =
  21. 21.682 − 466 =
  22. 22.792 − 588 =
  23. 23.477 − 361 =
  24. 24.313 + 556 =
  25. 25.471 + 608 =
  26. 26.451 − 285 =
  27. 27.459 + 352 =
  28. 28.603 + 599 =
  29. 29.188 + 585 =
  30. 30.375 + 311 =
  31. 31.640 + 491 =
  32. 32.445 + 407 =
  33. 33.798 − 509 =
  34. 34.415 − 171 =
  35. 35.580 + 221 =
  36. 36.498 + 572 =
  37. 37.323 + 236 =
  38. 38.692 − 232 =
  39. 39.294 + 616 =
  40. 40.232 + 593 =

Answer key

  1. 975
  2. 329
  3. 900
  4. 1345
  5. 246
  6. 1334
  7. 989
  8. 1259
  9. 456
  10. 723
  11. 305
  12. 851
  13. 1179
  14. 688
  15. 773
  16. 842
  17. 481
  18. 551
  19. 502
  20. 368
  21. 216
  22. 204
  23. 116
  24. 869
  25. 1079
  26. 166
  27. 811
  28. 1202
  29. 773
  30. 686
  31. 1131
  32. 852
  33. 289
  34. 244
  35. 801
  36. 1070
  37. 559
  38. 460
  39. 910
  40. 825

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