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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 454 · 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. 1.534 − 138 =
  2. 2.780 − 112 =
  3. 3.770 − 603 =
  4. 4.150 + 315 =
  5. 5.612 + 537 =
  6. 6.553 − 408 =
  7. 7.756 + 659 =
  8. 8.304 + 511 =
  9. 9.719 − 299 =
  10. 10.646 + 401 =
  11. 11.214 + 222 =
  12. 12.976 − 431 =
  13. 13.165 + 292 =
  14. 14.699 − 586 =
  15. 15.530 − 179 =
  16. 16.924 − 756 =
  17. 17.518 + 192 =
  18. 18.853 − 328 =
  19. 19.520 − 241 =
  20. 20.559 − 184 =
  21. 21.957 − 452 =
  22. 22.887 − 726 =
  23. 23.736 − 204 =
  24. 24.542 + 452 =
  25. 25.538 − 138 =
  26. 26.617 − 181 =
  27. 27.797 − 156 =
  28. 28.493 − 321 =
  29. 29.709 + 505 =
  30. 30.476 − 151 =
  31. 31.971 − 271 =
  32. 32.521 + 357 =
  33. 33.432 − 286 =
  34. 34.244 + 248 =
  35. 35.619 + 256 =
  36. 36.587 + 662 =
  37. 37.479 − 339 =
  38. 38.693 + 366 =
  39. 39.657 + 606 =
  40. 40.343 + 316 =

Answer key

  1. 396
  2. 668
  3. 167
  4. 465
  5. 1149
  6. 145
  7. 1415
  8. 815
  9. 420
  10. 1047
  11. 436
  12. 545
  13. 457
  14. 113
  15. 351
  16. 168
  17. 710
  18. 525
  19. 279
  20. 375
  21. 505
  22. 161
  23. 532
  24. 994
  25. 400
  26. 436
  27. 641
  28. 172
  29. 1214
  30. 325
  31. 700
  32. 878
  33. 146
  34. 492
  35. 875
  36. 1249
  37. 140
  38. 1059
  39. 1263
  40. 659

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