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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 173 · 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. 1.716 + 158 =
  2. 2.658 − 349 =
  3. 3.943 − 839 =
  4. 4.454 − 243 =
  5. 5.738 + 126 =
  6. 6.321 + 326 =
  7. 7.310 + 227 =
  8. 8.289 + 608 =
  9. 9.661 + 352 =
  10. 10.382 + 417 =
  11. 11.445 + 238 =
  12. 12.402 + 467 =
  13. 13.585 + 663 =
  14. 14.606 − 469 =
  15. 15.584 − 419 =
  16. 16.486 − 207 =
  17. 17.157 + 396 =
  18. 18.922 − 503 =
  19. 19.545 + 245 =
  20. 20.640 + 521 =
  21. 21.759 − 292 =
  22. 22.164 + 544 =
  23. 23.764 − 354 =
  24. 24.758 + 341 =
  25. 25.763 + 432 =
  26. 26.764 − 617 =
  27. 27.592 + 516 =
  28. 28.535 − 151 =
  29. 29.217 + 505 =
  30. 30.605 − 181 =
  31. 31.236 + 367 =
  32. 32.722 + 353 =
  33. 33.600 + 542 =
  34. 34.547 + 286 =
  35. 35.507 + 543 =
  36. 36.234 + 586 =
  37. 37.738 + 551 =
  38. 38.558 + 681 =
  39. 39.577 + 176 =
  40. 40.302 + 131 =

Answer key

  1. 874
  2. 309
  3. 104
  4. 211
  5. 864
  6. 647
  7. 537
  8. 897
  9. 1013
  10. 799
  11. 683
  12. 869
  13. 1248
  14. 137
  15. 165
  16. 279
  17. 553
  18. 419
  19. 790
  20. 1161
  21. 467
  22. 708
  23. 410
  24. 1099
  25. 1195
  26. 147
  27. 1108
  28. 384
  29. 722
  30. 424
  31. 603
  32. 1075
  33. 1142
  34. 833
  35. 1050
  36. 820
  37. 1289
  38. 1239
  39. 753
  40. 433

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