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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 264 · 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. 1.467 − 112 =
  2. 2.672 + 328 =
  3. 3.748 + 378 =
  4. 4.738 + 657 =
  5. 5.305 + 336 =
  6. 6.228 + 581 =
  7. 7.388 + 326 =
  8. 8.221 + 579 =
  9. 9.498 − 192 =
  10. 10.720 − 502 =
  11. 11.647 − 497 =
  12. 12.249 + 271 =
  13. 13.413 + 316 =
  14. 14.444 − 305 =
  15. 15.678 + 501 =
  16. 16.393 + 355 =
  17. 17.675 + 377 =
  18. 18.924 − 419 =
  19. 19.837 − 443 =
  20. 20.740 − 222 =
  21. 21.667 − 415 =
  22. 22.448 + 334 =
  23. 23.748 + 541 =
  24. 24.214 + 604 =
  25. 25.499 + 169 =
  26. 26.594 + 571 =
  27. 27.693 − 243 =
  28. 28.631 − 252 =
  29. 29.202 + 125 =
  30. 30.611 − 285 =
  31. 31.520 + 666 =
  32. 32.519 − 253 =
  33. 33.345 + 485 =
  34. 34.457 − 326 =
  35. 35.651 + 652 =
  36. 36.209 + 669 =
  37. 37.314 + 415 =
  38. 38.883 − 258 =
  39. 39.905 − 435 =
  40. 40.543 + 672 =

Answer key

  1. 355
  2. 1000
  3. 1126
  4. 1395
  5. 641
  6. 809
  7. 714
  8. 800
  9. 306
  10. 218
  11. 150
  12. 520
  13. 729
  14. 139
  15. 1179
  16. 748
  17. 1052
  18. 505
  19. 394
  20. 518
  21. 252
  22. 782
  23. 1289
  24. 818
  25. 668
  26. 1165
  27. 450
  28. 379
  29. 327
  30. 326
  31. 1186
  32. 266
  33. 830
  34. 131
  35. 1303
  36. 878
  37. 729
  38. 625
  39. 470
  40. 1215

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