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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 70 · 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. 1.323 + 542 =
  2. 2.900 − 448 =
  3. 3.138 + 246 =
  4. 4.142 + 216 =
  5. 5.924 − 697 =
  6. 6.581 − 372 =
  7. 7.235 + 423 =
  8. 8.724 + 469 =
  9. 9.894 − 597 =
  10. 10.460 + 131 =
  11. 11.629 − 266 =
  12. 12.275 + 213 =
  13. 13.536 − 164 =
  14. 14.529 − 123 =
  15. 15.696 + 299 =
  16. 16.361 + 463 =
  17. 17.393 + 138 =
  18. 18.407 + 352 =
  19. 19.365 + 141 =
  20. 20.550 + 669 =
  21. 21.527 + 298 =
  22. 22.409 + 359 =
  23. 23.139 + 423 =
  24. 24.703 − 155 =
  25. 25.437 − 326 =
  26. 26.499 − 291 =
  27. 27.809 − 192 =
  28. 28.127 + 501 =
  29. 29.442 + 188 =
  30. 30.196 + 301 =
  31. 31.445 + 371 =
  32. 32.437 − 279 =
  33. 33.390 + 571 =
  34. 34.756 − 267 =
  35. 35.846 − 381 =
  36. 36.754 − 267 =
  37. 37.466 + 237 =
  38. 38.512 − 224 =
  39. 39.967 − 793 =
  40. 40.373 + 656 =

Answer key

  1. 865
  2. 452
  3. 384
  4. 358
  5. 227
  6. 209
  7. 658
  8. 1193
  9. 297
  10. 591
  11. 363
  12. 488
  13. 372
  14. 406
  15. 995
  16. 824
  17. 531
  18. 759
  19. 506
  20. 1219
  21. 825
  22. 768
  23. 562
  24. 548
  25. 111
  26. 208
  27. 617
  28. 628
  29. 630
  30. 497
  31. 816
  32. 158
  33. 961
  34. 489
  35. 465
  36. 487
  37. 703
  38. 288
  39. 174
  40. 1029

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