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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 303 · 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. 1.709 − 374 =
  2. 2.920 − 306 =
  3. 3.580 + 178 =
  4. 4.466 + 619 =
  5. 5.845 − 265 =
  6. 6.702 + 677 =
  7. 7.217 + 448 =
  8. 8.201 + 577 =
  9. 9.581 + 445 =
  10. 10.788 + 506 =
  11. 11.404 + 344 =
  12. 12.456 + 244 =
  13. 13.506 − 164 =
  14. 14.922 − 737 =
  15. 15.504 + 364 =
  16. 16.436 + 416 =
  17. 17.616 + 263 =
  18. 18.806 − 251 =
  19. 19.582 − 417 =
  20. 20.152 + 629 =
  21. 21.618 + 379 =
  22. 22.590 − 327 =
  23. 23.546 − 113 =
  24. 24.387 + 669 =
  25. 25.563 + 371 =
  26. 26.614 + 216 =
  27. 27.256 + 151 =
  28. 28.608 + 599 =
  29. 29.972 − 483 =
  30. 30.826 − 457 =
  31. 31.392 + 618 =
  32. 32.235 + 518 =
  33. 33.530 + 296 =
  34. 34.492 + 148 =
  35. 35.232 + 192 =
  36. 36.739 − 431 =
  37. 37.334 + 314 =
  38. 38.594 + 589 =
  39. 39.470 + 262 =
  40. 40.659 + 128 =

Answer key

  1. 335
  2. 614
  3. 758
  4. 1085
  5. 580
  6. 1379
  7. 665
  8. 778
  9. 1026
  10. 1294
  11. 748
  12. 700
  13. 342
  14. 185
  15. 868
  16. 852
  17. 879
  18. 555
  19. 165
  20. 781
  21. 997
  22. 263
  23. 433
  24. 1056
  25. 934
  26. 830
  27. 407
  28. 1207
  29. 489
  30. 369
  31. 1010
  32. 753
  33. 826
  34. 640
  35. 424
  36. 308
  37. 648
  38. 1183
  39. 732
  40. 787

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