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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 371 · 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. 1.718 + 371 =
  2. 2.855 − 529 =
  3. 3.506 − 162 =
  4. 4.382 + 305 =
  5. 5.179 + 281 =
  6. 6.765 − 287 =
  7. 7.779 + 431 =
  8. 8.203 + 253 =
  9. 9.585 + 338 =
  10. 10.234 + 415 =
  11. 11.488 − 121 =
  12. 12.825 − 153 =
  13. 13.723 − 199 =
  14. 14.422 − 185 =
  15. 15.743 + 114 =
  16. 16.616 − 199 =
  17. 17.516 + 282 =
  18. 18.709 + 121 =
  19. 19.348 + 661 =
  20. 20.904 − 387 =
  21. 21.635 − 114 =
  22. 22.513 − 412 =
  23. 23.270 + 554 =
  24. 24.833 − 156 =
  25. 25.975 − 452 =
  26. 26.726 + 448 =
  27. 27.197 + 303 =
  28. 28.127 + 115 =
  29. 29.447 − 324 =
  30. 30.860 − 567 =
  31. 31.183 + 201 =
  32. 32.770 − 638 =
  33. 33.510 − 368 =
  34. 34.700 + 622 =
  35. 35.480 − 329 =
  36. 36.713 + 621 =
  37. 37.534 − 303 =
  38. 38.185 + 389 =
  39. 39.347 + 476 =
  40. 40.404 + 157 =

Answer key

  1. 1089
  2. 326
  3. 344
  4. 687
  5. 460
  6. 478
  7. 1210
  8. 456
  9. 923
  10. 649
  11. 367
  12. 672
  13. 524
  14. 237
  15. 857
  16. 417
  17. 798
  18. 830
  19. 1009
  20. 517
  21. 521
  22. 101
  23. 824
  24. 677
  25. 523
  26. 1174
  27. 500
  28. 242
  29. 123
  30. 293
  31. 384
  32. 132
  33. 142
  34. 1322
  35. 151
  36. 1334
  37. 231
  38. 574
  39. 823
  40. 561

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