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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 135 · 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. 1.301 + 659 =
  2. 2.593 − 427 =
  3. 3.559 + 276 =
  4. 4.400 + 381 =
  5. 5.740 − 173 =
  6. 6.154 + 549 =
  7. 7.815 − 328 =
  8. 8.186 + 205 =
  9. 9.279 + 138 =
  10. 10.692 + 129 =
  11. 11.608 − 335 =
  12. 12.405 + 153 =
  13. 13.298 + 406 =
  14. 14.677 + 669 =
  15. 15.556 + 494 =
  16. 16.201 + 258 =
  17. 17.641 − 125 =
  18. 18.758 − 373 =
  19. 19.632 + 516 =
  20. 20.897 − 598 =
  21. 21.175 + 243 =
  22. 22.136 + 316 =
  23. 23.360 + 591 =
  24. 24.838 − 352 =
  25. 25.746 − 284 =
  26. 26.786 + 646 =
  27. 27.246 + 489 =
  28. 28.374 + 429 =
  29. 29.670 + 429 =
  30. 30.588 − 486 =
  31. 31.961 − 267 =
  32. 32.415 + 217 =
  33. 33.290 + 682 =
  34. 34.701 − 201 =
  35. 35.383 + 552 =
  36. 36.923 − 678 =
  37. 37.415 − 159 =
  38. 38.308 + 115 =
  39. 39.655 + 133 =
  40. 40.365 + 334 =

Answer key

  1. 960
  2. 166
  3. 835
  4. 781
  5. 567
  6. 703
  7. 487
  8. 391
  9. 417
  10. 821
  11. 273
  12. 558
  13. 704
  14. 1346
  15. 1050
  16. 459
  17. 516
  18. 385
  19. 1148
  20. 299
  21. 418
  22. 452
  23. 951
  24. 486
  25. 462
  26. 1432
  27. 735
  28. 803
  29. 1099
  30. 102
  31. 694
  32. 632
  33. 972
  34. 500
  35. 935
  36. 245
  37. 256
  38. 423
  39. 788
  40. 699

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