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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 850 · 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. 1.346 + 646 =
  2. 2.766 − 199 =
  3. 3.511 − 125 =
  4. 4.623 − 441 =
  5. 5.746 + 471 =
  6. 6.421 + 643 =
  7. 7.770 − 113 =
  8. 8.632 − 328 =
  9. 9.548 + 133 =
  10. 10.403 + 176 =
  11. 11.217 + 563 =
  12. 12.847 − 631 =
  13. 13.164 + 123 =
  14. 14.506 + 149 =
  15. 15.591 − 465 =
  16. 16.248 + 681 =
  17. 17.543 − 396 =
  18. 18.909 − 765 =
  19. 19.464 − 359 =
  20. 20.165 + 124 =
  21. 21.551 + 644 =
  22. 22.706 + 161 =
  23. 23.693 + 657 =
  24. 24.424 − 304 =
  25. 25.318 + 598 =
  26. 26.213 + 245 =
  27. 27.856 − 389 =
  28. 28.888 − 517 =
  29. 29.737 − 285 =
  30. 30.513 − 395 =
  31. 31.649 + 599 =
  32. 32.741 − 116 =
  33. 33.247 + 193 =
  34. 34.501 + 154 =
  35. 35.781 + 307 =
  36. 36.269 + 257 =
  37. 37.841 − 187 =
  38. 38.448 + 263 =
  39. 39.733 + 646 =
  40. 40.126 + 517 =

Answer key

  1. 992
  2. 567
  3. 386
  4. 182
  5. 1217
  6. 1064
  7. 657
  8. 304
  9. 681
  10. 579
  11. 780
  12. 216
  13. 287
  14. 655
  15. 126
  16. 929
  17. 147
  18. 144
  19. 105
  20. 289
  21. 1195
  22. 867
  23. 1350
  24. 120
  25. 916
  26. 458
  27. 467
  28. 371
  29. 452
  30. 118
  31. 1248
  32. 625
  33. 440
  34. 655
  35. 1088
  36. 526
  37. 654
  38. 711
  39. 1379
  40. 643

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