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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 159 · 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. 1.710 + 511 =
  2. 2.427 + 601 =
  3. 3.935 − 715 =
  4. 4.625 + 634 =
  5. 5.787 − 631 =
  6. 6.454 + 439 =
  7. 7.625 − 145 =
  8. 8.419 + 185 =
  9. 9.571 + 253 =
  10. 10.725 − 247 =
  11. 11.415 − 134 =
  12. 12.722 + 351 =
  13. 13.174 + 439 =
  14. 14.554 − 242 =
  15. 15.702 − 363 =
  16. 16.457 − 256 =
  17. 17.637 + 588 =
  18. 18.902 − 614 =
  19. 19.496 − 337 =
  20. 20.468 + 413 =
  21. 21.751 − 457 =
  22. 22.582 − 396 =
  23. 23.525 + 273 =
  24. 24.443 + 522 =
  25. 25.632 + 524 =
  26. 26.206 + 531 =
  27. 27.985 − 528 =
  28. 28.731 − 336 =
  29. 29.726 − 226 =
  30. 30.687 − 254 =
  31. 31.753 − 592 =
  32. 32.630 + 161 =
  33. 33.559 − 387 =
  34. 34.468 + 261 =
  35. 35.678 + 657 =
  36. 36.432 + 163 =
  37. 37.600 + 197 =
  38. 38.331 + 244 =
  39. 39.456 − 285 =
  40. 40.425 + 547 =

Answer key

  1. 1221
  2. 1028
  3. 220
  4. 1259
  5. 156
  6. 893
  7. 480
  8. 604
  9. 824
  10. 478
  11. 281
  12. 1073
  13. 613
  14. 312
  15. 339
  16. 201
  17. 1225
  18. 288
  19. 159
  20. 881
  21. 294
  22. 186
  23. 798
  24. 965
  25. 1156
  26. 737
  27. 457
  28. 395
  29. 500
  30. 433
  31. 161
  32. 791
  33. 172
  34. 729
  35. 1335
  36. 595
  37. 797
  38. 575
  39. 171
  40. 972

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