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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 634 · 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. 1.775 − 133 =
  2. 2.692 + 654 =
  3. 3.787 + 374 =
  4. 4.612 − 171 =
  5. 5.838 − 708 =
  6. 6.690 − 221 =
  7. 7.138 + 471 =
  8. 8.665 − 194 =
  9. 9.832 − 339 =
  10. 10.662 + 658 =
  11. 11.548 − 238 =
  12. 12.589 − 454 =
  13. 13.981 − 635 =
  14. 14.533 + 388 =
  15. 15.475 − 157 =
  16. 16.921 − 735 =
  17. 17.415 + 656 =
  18. 18.583 + 514 =
  19. 19.417 + 442 =
  20. 20.202 + 121 =
  21. 21.624 + 542 =
  22. 22.168 + 299 =
  23. 23.726 + 371 =
  24. 24.363 + 167 =
  25. 25.198 + 207 =
  26. 26.365 + 447 =
  27. 27.787 + 291 =
  28. 28.442 + 263 =
  29. 29.788 + 301 =
  30. 30.743 + 628 =
  31. 31.669 − 305 =
  32. 32.538 + 399 =
  33. 33.450 + 228 =
  34. 34.421 + 242 =
  35. 35.244 + 301 =
  36. 36.987 − 581 =
  37. 37.634 − 169 =
  38. 38.370 + 121 =
  39. 39.515 − 164 =
  40. 40.567 + 536 =

Answer key

  1. 642
  2. 1346
  3. 1161
  4. 441
  5. 130
  6. 469
  7. 609
  8. 471
  9. 493
  10. 1320
  11. 310
  12. 135
  13. 346
  14. 921
  15. 318
  16. 186
  17. 1071
  18. 1097
  19. 859
  20. 323
  21. 1166
  22. 467
  23. 1097
  24. 530
  25. 405
  26. 812
  27. 1078
  28. 705
  29. 1089
  30. 1371
  31. 364
  32. 937
  33. 678
  34. 663
  35. 545
  36. 406
  37. 465
  38. 491
  39. 351
  40. 1103

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