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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 418 · 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. 1.275 + 601 =
  2. 2.693 − 151 =
  3. 3.369 + 601 =
  4. 4.644 + 221 =
  5. 5.711 + 181 =
  6. 6.366 + 301 =
  7. 7.482 − 277 =
  8. 8.931 − 411 =
  9. 9.434 + 147 =
  10. 10.560 − 133 =
  11. 11.449 + 576 =
  12. 12.707 + 528 =
  13. 13.521 − 341 =
  14. 14.641 − 289 =
  15. 15.750 + 282 =
  16. 16.183 + 169 =
  17. 17.517 + 361 =
  18. 18.515 + 119 =
  19. 19.132 + 245 =
  20. 20.739 − 123 =
  21. 21.650 − 311 =
  22. 22.417 − 305 =
  23. 23.527 − 151 =
  24. 24.729 − 169 =
  25. 25.758 + 543 =
  26. 26.444 − 189 =
  27. 27.324 + 139 =
  28. 28.734 − 405 =
  29. 29.832 − 471 =
  30. 30.847 − 509 =
  31. 31.908 − 807 =
  32. 32.493 − 152 =
  33. 33.745 + 455 =
  34. 34.616 − 231 =
  35. 35.723 + 384 =
  36. 36.857 − 125 =
  37. 37.270 + 454 =
  38. 38.829 − 616 =
  39. 39.170 + 558 =
  40. 40.652 − 125 =

Answer key

  1. 876
  2. 542
  3. 970
  4. 865
  5. 892
  6. 667
  7. 205
  8. 520
  9. 581
  10. 427
  11. 1025
  12. 1235
  13. 180
  14. 352
  15. 1032
  16. 352
  17. 878
  18. 634
  19. 377
  20. 616
  21. 339
  22. 112
  23. 376
  24. 560
  25. 1301
  26. 255
  27. 463
  28. 329
  29. 361
  30. 338
  31. 101
  32. 341
  33. 1200
  34. 385
  35. 1107
  36. 732
  37. 724
  38. 213
  39. 728
  40. 527

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