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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 143 · 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. 1.187 + 461 =
  2. 2.373 + 507 =
  3. 3.262 + 386 =
  4. 4.906 − 132 =
  5. 5.323 + 457 =
  6. 6.817 − 665 =
  7. 7.904 − 526 =
  8. 8.557 − 413 =
  9. 9.825 − 166 =
  10. 10.457 − 159 =
  11. 11.541 − 169 =
  12. 12.682 − 266 =
  13. 13.423 − 261 =
  14. 14.563 − 164 =
  15. 15.855 − 718 =
  16. 16.582 − 341 =
  17. 17.754 − 269 =
  18. 18.261 + 294 =
  19. 19.657 + 252 =
  20. 20.479 − 337 =
  21. 21.884 − 685 =
  22. 22.364 + 168 =
  23. 23.285 + 393 =
  24. 24.262 + 452 =
  25. 25.638 − 503 =
  26. 26.736 − 184 =
  27. 27.778 + 653 =
  28. 28.515 + 415 =
  29. 29.491 − 291 =
  30. 30.926 − 768 =
  31. 31.560 + 135 =
  32. 32.697 + 495 =
  33. 33.733 + 297 =
  34. 34.398 + 231 =
  35. 35.892 − 251 =
  36. 36.407 + 344 =
  37. 37.239 + 281 =
  38. 38.434 − 236 =
  39. 39.227 + 487 =
  40. 40.627 + 433 =

Answer key

  1. 648
  2. 880
  3. 648
  4. 774
  5. 780
  6. 152
  7. 378
  8. 144
  9. 659
  10. 298
  11. 372
  12. 416
  13. 162
  14. 399
  15. 137
  16. 241
  17. 485
  18. 555
  19. 909
  20. 142
  21. 199
  22. 532
  23. 678
  24. 714
  25. 135
  26. 552
  27. 1431
  28. 930
  29. 200
  30. 158
  31. 695
  32. 1192
  33. 1030
  34. 629
  35. 641
  36. 751
  37. 520
  38. 198
  39. 714
  40. 1060

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