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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 509 · 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. 1.497 + 588 =
  2. 2.150 + 572 =
  3. 3.214 + 486 =
  4. 4.843 − 553 =
  5. 5.737 + 581 =
  6. 6.647 − 243 =
  7. 7.635 + 138 =
  8. 8.448 + 238 =
  9. 9.801 − 362 =
  10. 10.150 + 644 =
  11. 11.518 − 276 =
  12. 12.546 + 465 =
  13. 13.630 − 346 =
  14. 14.946 − 564 =
  15. 15.881 − 601 =
  16. 16.648 + 294 =
  17. 17.140 + 171 =
  18. 18.553 + 446 =
  19. 19.716 − 176 =
  20. 20.712 + 214 =
  21. 21.445 + 272 =
  22. 22.190 + 438 =
  23. 23.949 − 658 =
  24. 24.327 + 281 =
  25. 25.750 − 245 =
  26. 26.813 − 282 =
  27. 27.868 − 454 =
  28. 28.621 − 118 =
  29. 29.780 + 186 =
  30. 30.701 + 454 =
  31. 31.819 − 307 =
  32. 32.763 + 223 =
  33. 33.897 − 402 =
  34. 34.817 − 432 =
  35. 35.451 − 271 =
  36. 36.465 − 285 =
  37. 37.388 + 673 =
  38. 38.543 − 211 =
  39. 39.413 + 561 =
  40. 40.533 − 117 =

Answer key

  1. 1085
  2. 722
  3. 700
  4. 290
  5. 1318
  6. 404
  7. 773
  8. 686
  9. 439
  10. 794
  11. 242
  12. 1011
  13. 284
  14. 382
  15. 280
  16. 942
  17. 311
  18. 999
  19. 540
  20. 926
  21. 717
  22. 628
  23. 291
  24. 608
  25. 505
  26. 531
  27. 414
  28. 503
  29. 966
  30. 1155
  31. 512
  32. 986
  33. 495
  34. 385
  35. 180
  36. 180
  37. 1061
  38. 332
  39. 974
  40. 416

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