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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 362 · 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. 1.219 + 115 =
  2. 2.496 − 143 =
  3. 3.672 − 406 =
  4. 4.622 − 331 =
  5. 5.459 − 261 =
  6. 6.703 + 512 =
  7. 7.487 + 637 =
  8. 8.645 + 249 =
  9. 9.528 − 118 =
  10. 10.624 + 445 =
  11. 11.785 + 261 =
  12. 12.669 − 455 =
  13. 13.236 + 211 =
  14. 14.487 − 238 =
  15. 15.654 + 487 =
  16. 16.515 + 176 =
  17. 17.573 − 216 =
  18. 18.297 + 522 =
  19. 19.428 − 301 =
  20. 20.381 + 229 =
  21. 21.849 − 292 =
  22. 22.931 − 229 =
  23. 23.868 − 568 =
  24. 24.826 − 496 =
  25. 25.453 − 145 =
  26. 26.550 + 459 =
  27. 27.867 − 761 =
  28. 28.561 + 147 =
  29. 29.630 − 511 =
  30. 30.733 + 396 =
  31. 31.238 + 497 =
  32. 32.541 + 184 =
  33. 33.286 + 289 =
  34. 34.123 + 543 =
  35. 35.272 + 658 =
  36. 36.693 + 539 =
  37. 37.773 + 246 =
  38. 38.394 + 194 =
  39. 39.457 + 439 =
  40. 40.487 + 141 =

Answer key

  1. 334
  2. 353
  3. 266
  4. 291
  5. 198
  6. 1215
  7. 1124
  8. 894
  9. 410
  10. 1069
  11. 1046
  12. 214
  13. 447
  14. 249
  15. 1141
  16. 691
  17. 357
  18. 819
  19. 127
  20. 610
  21. 557
  22. 702
  23. 300
  24. 330
  25. 308
  26. 1009
  27. 106
  28. 708
  29. 119
  30. 1129
  31. 735
  32. 725
  33. 575
  34. 666
  35. 930
  36. 1232
  37. 1019
  38. 588
  39. 896
  40. 628

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