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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 637 · 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. 1.342 + 122 =
  2. 2.530 − 127 =
  3. 3.983 − 292 =
  4. 4.597 + 251 =
  5. 5.589 + 559 =
  6. 6.690 − 276 =
  7. 7.934 − 421 =
  8. 8.758 + 578 =
  9. 9.880 − 167 =
  10. 10.302 + 577 =
  11. 11.754 + 451 =
  12. 12.470 − 275 =
  13. 13.492 − 377 =
  14. 14.501 + 503 =
  15. 15.616 + 208 =
  16. 16.192 + 135 =
  17. 17.404 + 165 =
  18. 18.212 + 548 =
  19. 19.493 − 124 =
  20. 20.719 + 176 =
  21. 21.738 − 552 =
  22. 22.612 + 304 =
  23. 23.869 − 442 =
  24. 24.697 − 465 =
  25. 25.143 + 292 =
  26. 26.214 + 594 =
  27. 27.267 + 354 =
  28. 28.421 + 449 =
  29. 29.788 + 484 =
  30. 30.665 + 462 =
  31. 31.533 + 444 =
  32. 32.354 + 373 =
  33. 33.645 + 367 =
  34. 34.484 + 475 =
  35. 35.898 − 117 =
  36. 36.528 − 211 =
  37. 37.647 + 645 =
  38. 38.565 + 614 =
  39. 39.836 − 235 =
  40. 40.824 − 684 =

Answer key

  1. 464
  2. 403
  3. 691
  4. 848
  5. 1148
  6. 414
  7. 513
  8. 1336
  9. 713
  10. 879
  11. 1205
  12. 195
  13. 115
  14. 1004
  15. 824
  16. 327
  17. 569
  18. 760
  19. 369
  20. 895
  21. 186
  22. 916
  23. 427
  24. 232
  25. 435
  26. 808
  27. 621
  28. 870
  29. 1272
  30. 1127
  31. 977
  32. 727
  33. 1012
  34. 959
  35. 781
  36. 317
  37. 1292
  38. 1179
  39. 601
  40. 140

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