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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 635 · 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. 1.536 − 251 =
  2. 2.129 + 138 =
  3. 3.902 − 298 =
  4. 4.318 + 155 =
  5. 5.786 − 331 =
  6. 6.143 + 474 =
  7. 7.486 + 608 =
  8. 8.604 − 491 =
  9. 9.643 − 268 =
  10. 10.548 − 119 =
  11. 11.229 + 445 =
  12. 12.898 − 307 =
  13. 13.536 + 634 =
  14. 14.599 + 624 =
  15. 15.937 − 311 =
  16. 16.537 − 408 =
  17. 17.499 + 318 =
  18. 18.393 + 209 =
  19. 19.547 + 374 =
  20. 20.626 + 601 =
  21. 21.435 + 554 =
  22. 22.167 + 408 =
  23. 23.681 + 488 =
  24. 24.784 − 281 =
  25. 25.742 + 165 =
  26. 26.718 + 419 =
  27. 27.561 − 197 =
  28. 28.753 − 351 =
  29. 29.502 − 182 =
  30. 30.603 + 134 =
  31. 31.424 + 528 =
  32. 32.295 + 593 =
  33. 33.695 + 353 =
  34. 34.585 + 631 =
  35. 35.714 − 552 =
  36. 36.608 + 531 =
  37. 37.912 − 758 =
  38. 38.315 + 203 =
  39. 39.170 + 501 =
  40. 40.783 + 171 =

Answer key

  1. 285
  2. 267
  3. 604
  4. 473
  5. 455
  6. 617
  7. 1094
  8. 113
  9. 375
  10. 429
  11. 674
  12. 591
  13. 1170
  14. 1223
  15. 626
  16. 129
  17. 817
  18. 602
  19. 921
  20. 1227
  21. 989
  22. 575
  23. 1169
  24. 503
  25. 907
  26. 1137
  27. 364
  28. 402
  29. 320
  30. 737
  31. 952
  32. 888
  33. 1048
  34. 1216
  35. 162
  36. 1139
  37. 154
  38. 518
  39. 671
  40. 954

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