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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 655 · 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. 1.419 + 603 =
  2. 2.770 + 591 =
  3. 3.785 − 199 =
  4. 4.609 − 121 =
  5. 5.966 − 363 =
  6. 6.630 − 266 =
  7. 7.390 + 487 =
  8. 8.603 − 167 =
  9. 9.899 − 571 =
  10. 10.469 − 142 =
  11. 11.921 − 643 =
  12. 12.378 + 373 =
  13. 13.857 − 554 =
  14. 14.286 + 378 =
  15. 15.634 − 516 =
  16. 16.798 − 221 =
  17. 17.775 + 616 =
  18. 18.761 + 357 =
  19. 19.493 − 159 =
  20. 20.715 + 299 =
  21. 21.482 − 181 =
  22. 22.493 + 417 =
  23. 23.382 + 621 =
  24. 24.755 − 586 =
  25. 25.291 + 124 =
  26. 26.903 − 143 =
  27. 27.205 + 211 =
  28. 28.536 + 329 =
  29. 29.929 − 415 =
  30. 30.165 + 551 =
  31. 31.125 + 381 =
  32. 32.456 − 271 =
  33. 33.535 + 686 =
  34. 34.450 − 165 =
  35. 35.705 + 467 =
  36. 36.128 + 669 =
  37. 37.856 − 641 =
  38. 38.514 + 133 =
  39. 39.652 + 659 =
  40. 40.232 + 248 =

Answer key

  1. 1022
  2. 1361
  3. 586
  4. 488
  5. 603
  6. 364
  7. 877
  8. 436
  9. 328
  10. 327
  11. 278
  12. 751
  13. 303
  14. 664
  15. 118
  16. 577
  17. 1391
  18. 1118
  19. 334
  20. 1014
  21. 301
  22. 910
  23. 1003
  24. 169
  25. 415
  26. 760
  27. 416
  28. 865
  29. 514
  30. 716
  31. 506
  32. 185
  33. 1221
  34. 285
  35. 1172
  36. 797
  37. 215
  38. 647
  39. 1311
  40. 480

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