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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 975 · 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. 1.604 + 163 =
  2. 2.696 + 284 =
  3. 3.178 + 498 =
  4. 4.251 + 551 =
  5. 5.302 + 451 =
  6. 6.968 − 807 =
  7. 7.835 − 179 =
  8. 8.485 − 232 =
  9. 9.182 + 644 =
  10. 10.300 + 154 =
  11. 11.483 + 415 =
  12. 12.570 − 391 =
  13. 13.687 + 186 =
  14. 14.788 − 603 =
  15. 15.532 + 321 =
  16. 16.693 − 587 =
  17. 17.275 + 448 =
  18. 18.554 + 515 =
  19. 19.299 + 511 =
  20. 20.775 + 369 =
  21. 21.203 + 508 =
  22. 22.891 − 527 =
  23. 23.571 − 205 =
  24. 24.154 + 631 =
  25. 25.633 − 283 =
  26. 26.629 − 202 =
  27. 27.561 − 442 =
  28. 28.423 + 415 =
  29. 29.698 + 427 =
  30. 30.782 − 361 =
  31. 31.506 − 144 =
  32. 32.630 + 537 =
  33. 33.629 − 233 =
  34. 34.875 − 513 =
  35. 35.592 + 281 =
  36. 36.595 − 421 =
  37. 37.157 + 569 =
  38. 38.623 − 126 =
  39. 39.852 − 377 =
  40. 40.902 − 416 =

Answer key

  1. 767
  2. 980
  3. 676
  4. 802
  5. 753
  6. 161
  7. 656
  8. 253
  9. 826
  10. 454
  11. 898
  12. 179
  13. 873
  14. 185
  15. 853
  16. 106
  17. 723
  18. 1069
  19. 810
  20. 1144
  21. 711
  22. 364
  23. 366
  24. 785
  25. 350
  26. 427
  27. 119
  28. 838
  29. 1125
  30. 421
  31. 362
  32. 1167
  33. 396
  34. 362
  35. 873
  36. 174
  37. 726
  38. 497
  39. 475
  40. 486

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