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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 253 · 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. 1.645 + 645 =
  2. 2.528 + 498 =
  3. 3.224 + 205 =
  4. 4.509 − 283 =
  5. 5.330 + 609 =
  6. 6.539 − 144 =
  7. 7.807 − 407 =
  8. 8.537 + 472 =
  9. 9.466 − 366 =
  10. 10.428 + 162 =
  11. 11.419 − 309 =
  12. 12.590 + 246 =
  13. 13.496 − 291 =
  14. 14.782 − 638 =
  15. 15.767 − 291 =
  16. 16.559 − 235 =
  17. 17.926 − 619 =
  18. 18.199 + 641 =
  19. 19.450 − 139 =
  20. 20.489 + 522 =
  21. 21.449 − 141 =
  22. 22.520 + 282 =
  23. 23.532 − 133 =
  24. 24.911 − 645 =
  25. 25.494 − 117 =
  26. 26.590 − 264 =
  27. 27.294 + 299 =
  28. 28.239 + 631 =
  29. 29.341 + 532 =
  30. 30.202 + 208 =
  31. 31.546 − 414 =
  32. 32.201 + 289 =
  33. 33.865 − 758 =
  34. 34.502 − 357 =
  35. 35.193 + 428 =
  36. 36.747 − 624 =
  37. 37.441 + 378 =
  38. 38.241 + 529 =
  39. 39.260 + 629 =
  40. 40.154 + 662 =

Answer key

  1. 1290
  2. 1026
  3. 429
  4. 226
  5. 939
  6. 395
  7. 400
  8. 1009
  9. 100
  10. 590
  11. 110
  12. 836
  13. 205
  14. 144
  15. 476
  16. 324
  17. 307
  18. 840
  19. 311
  20. 1011
  21. 308
  22. 802
  23. 399
  24. 266
  25. 377
  26. 326
  27. 593
  28. 870
  29. 873
  30. 410
  31. 132
  32. 490
  33. 107
  34. 145
  35. 621
  36. 123
  37. 819
  38. 770
  39. 889
  40. 816

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