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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 8 · 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. 1.297 + 658 =
  2. 2.566 + 528 =
  3. 3.387 + 503 =
  4. 4.205 + 278 =
  5. 5.575 + 276 =
  6. 6.745 − 276 =
  7. 7.521 − 191 =
  8. 8.561 + 366 =
  9. 9.701 − 499 =
  10. 10.553 − 138 =
  11. 11.460 + 351 =
  12. 12.657 + 493 =
  13. 13.241 + 266 =
  14. 14.679 + 323 =
  15. 15.573 + 647 =
  16. 16.808 − 258 =
  17. 17.914 − 311 =
  18. 18.844 − 444 =
  19. 19.650 + 317 =
  20. 20.353 + 575 =
  21. 21.763 − 592 =
  22. 22.524 − 303 =
  23. 23.132 + 236 =
  24. 24.210 + 587 =
  25. 25.560 − 287 =
  26. 26.965 − 159 =
  27. 27.575 − 442 =
  28. 28.667 + 113 =
  29. 29.251 + 141 =
  30. 30.720 + 221 =
  31. 31.509 − 281 =
  32. 32.690 − 397 =
  33. 33.599 − 147 =
  34. 34.297 + 491 =
  35. 35.455 − 271 =
  36. 36.594 + 621 =
  37. 37.785 − 177 =
  38. 38.298 + 426 =
  39. 39.200 + 375 =
  40. 40.208 + 525 =

Answer key

  1. 955
  2. 1094
  3. 890
  4. 483
  5. 851
  6. 469
  7. 330
  8. 927
  9. 202
  10. 415
  11. 811
  12. 1150
  13. 507
  14. 1002
  15. 1220
  16. 550
  17. 603
  18. 400
  19. 967
  20. 928
  21. 171
  22. 221
  23. 368
  24. 797
  25. 273
  26. 806
  27. 133
  28. 780
  29. 392
  30. 941
  31. 228
  32. 293
  33. 452
  34. 788
  35. 184
  36. 1215
  37. 608
  38. 724
  39. 575
  40. 733

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