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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 410 · 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. 1.649 + 629 =
  2. 2.767 + 133 =
  3. 3.185 + 622 =
  4. 4.255 + 678 =
  5. 5.151 + 654 =
  6. 6.957 − 319 =
  7. 7.223 + 388 =
  8. 8.593 + 242 =
  9. 9.532 + 476 =
  10. 10.439 + 132 =
  11. 11.729 + 169 =
  12. 12.504 − 121 =
  13. 13.757 − 385 =
  14. 14.467 + 518 =
  15. 15.246 + 277 =
  16. 16.656 + 424 =
  17. 17.606 − 259 =
  18. 18.740 + 279 =
  19. 19.628 − 357 =
  20. 20.551 + 473 =
  21. 21.521 + 227 =
  22. 22.686 + 599 =
  23. 23.586 + 208 =
  24. 24.511 + 213 =
  25. 25.952 − 202 =
  26. 26.226 + 336 =
  27. 27.728 + 397 =
  28. 28.942 − 115 =
  29. 29.810 − 161 =
  30. 30.566 − 155 =
  31. 31.589 + 676 =
  32. 32.967 − 292 =
  33. 33.703 − 264 =
  34. 34.965 − 415 =
  35. 35.387 + 602 =
  36. 36.557 − 367 =
  37. 37.904 − 473 =
  38. 38.548 + 356 =
  39. 39.815 − 189 =
  40. 40.448 + 291 =

Answer key

  1. 1278
  2. 900
  3. 807
  4. 933
  5. 805
  6. 638
  7. 611
  8. 835
  9. 1008
  10. 571
  11. 898
  12. 383
  13. 372
  14. 985
  15. 523
  16. 1080
  17. 347
  18. 1019
  19. 271
  20. 1024
  21. 748
  22. 1285
  23. 794
  24. 724
  25. 750
  26. 562
  27. 1125
  28. 827
  29. 649
  30. 411
  31. 1265
  32. 675
  33. 439
  34. 550
  35. 989
  36. 190
  37. 431
  38. 904
  39. 626
  40. 739

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