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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 743 · 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. 1.421 − 142 =
  2. 2.730 − 594 =
  3. 3.550 + 191 =
  4. 4.983 − 168 =
  5. 5.527 − 231 =
  6. 6.691 − 169 =
  7. 7.520 − 137 =
  8. 8.210 + 181 =
  9. 9.303 + 347 =
  10. 10.484 + 683 =
  11. 11.709 + 208 =
  12. 12.904 − 478 =
  13. 13.523 − 313 =
  14. 14.427 + 297 =
  15. 15.889 − 152 =
  16. 16.915 − 793 =
  17. 17.405 + 421 =
  18. 18.506 − 155 =
  19. 19.364 + 501 =
  20. 20.474 + 328 =
  21. 21.913 − 472 =
  22. 22.612 − 391 =
  23. 23.316 + 158 =
  24. 24.506 − 149 =
  25. 25.210 + 157 =
  26. 26.262 + 238 =
  27. 27.934 − 208 =
  28. 28.438 − 117 =
  29. 29.455 + 403 =
  30. 30.432 + 275 =
  31. 31.683 − 141 =
  32. 32.516 + 181 =
  33. 33.140 + 159 =
  34. 34.541 + 421 =
  35. 35.842 − 526 =
  36. 36.791 − 633 =
  37. 37.625 + 498 =
  38. 38.498 − 368 =
  39. 39.457 + 142 =
  40. 40.932 − 405 =

Answer key

  1. 279
  2. 136
  3. 741
  4. 815
  5. 296
  6. 522
  7. 383
  8. 391
  9. 650
  10. 1167
  11. 917
  12. 426
  13. 210
  14. 724
  15. 737
  16. 122
  17. 826
  18. 351
  19. 865
  20. 802
  21. 441
  22. 221
  23. 474
  24. 357
  25. 367
  26. 500
  27. 726
  28. 321
  29. 858
  30. 707
  31. 542
  32. 697
  33. 299
  34. 962
  35. 316
  36. 158
  37. 1123
  38. 130
  39. 599
  40. 527

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