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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 149 · 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 + 118 =
  2. 2.760 + 674 =
  3. 3.149 + 591 =
  4. 4.358 + 531 =
  5. 5.748 + 631 =
  6. 6.144 + 517 =
  7. 7.251 + 508 =
  8. 8.452 + 618 =
  9. 9.732 + 237 =
  10. 10.722 + 434 =
  11. 11.169 + 458 =
  12. 12.527 − 156 =
  13. 13.190 + 545 =
  14. 14.559 − 341 =
  15. 15.591 − 166 =
  16. 16.282 + 608 =
  17. 17.760 − 233 =
  18. 18.520 + 447 =
  19. 19.862 − 643 =
  20. 20.637 + 177 =
  21. 21.201 + 613 =
  22. 22.689 + 397 =
  23. 23.763 − 261 =
  24. 24.985 − 736 =
  25. 25.736 + 411 =
  26. 26.948 − 371 =
  27. 27.597 + 474 =
  28. 28.581 − 472 =
  29. 29.542 + 155 =
  30. 30.875 − 256 =
  31. 31.625 + 159 =
  32. 32.294 + 331 =
  33. 33.549 + 597 =
  34. 34.361 + 141 =
  35. 35.723 − 348 =
  36. 36.327 + 688 =
  37. 37.526 + 615 =
  38. 38.918 − 614 =
  39. 39.537 + 224 =
  40. 40.831 − 339 =

Answer key

  1. 460
  2. 1434
  3. 740
  4. 889
  5. 1379
  6. 661
  7. 759
  8. 1070
  9. 969
  10. 1156
  11. 627
  12. 371
  13. 735
  14. 218
  15. 425
  16. 890
  17. 527
  18. 967
  19. 219
  20. 814
  21. 814
  22. 1086
  23. 502
  24. 249
  25. 1147
  26. 577
  27. 1071
  28. 109
  29. 697
  30. 619
  31. 784
  32. 625
  33. 1146
  34. 502
  35. 375
  36. 1015
  37. 1141
  38. 304
  39. 761
  40. 492

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