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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 993 · 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. 1.703 + 453 =
  2. 2.508 + 132 =
  3. 3.538 − 144 =
  4. 4.920 − 667 =
  5. 5.657 − 163 =
  6. 6.613 + 537 =
  7. 7.745 + 345 =
  8. 8.202 + 141 =
  9. 9.565 + 368 =
  10. 10.779 + 466 =
  11. 11.566 + 566 =
  12. 12.602 − 312 =
  13. 13.787 − 425 =
  14. 14.201 + 455 =
  15. 15.142 + 682 =
  16. 16.483 − 371 =
  17. 17.220 + 659 =
  18. 18.652 + 658 =
  19. 19.664 + 184 =
  20. 20.735 + 239 =
  21. 21.898 − 142 =
  22. 22.942 − 164 =
  23. 23.511 − 402 =
  24. 24.681 + 645 =
  25. 25.759 + 669 =
  26. 26.844 − 174 =
  27. 27.787 + 219 =
  28. 28.727 − 555 =
  29. 29.554 + 164 =
  30. 30.500 − 326 =
  31. 31.473 + 611 =
  32. 32.410 + 559 =
  33. 33.283 + 588 =
  34. 34.760 − 233 =
  35. 35.540 + 127 =
  36. 36.539 − 261 =
  37. 37.769 + 504 =
  38. 38.289 + 601 =
  39. 39.591 − 213 =
  40. 40.638 − 168 =

Answer key

  1. 1156
  2. 640
  3. 394
  4. 253
  5. 494
  6. 1150
  7. 1090
  8. 343
  9. 933
  10. 1245
  11. 1132
  12. 290
  13. 362
  14. 656
  15. 824
  16. 112
  17. 879
  18. 1310
  19. 848
  20. 974
  21. 756
  22. 778
  23. 109
  24. 1326
  25. 1428
  26. 670
  27. 1006
  28. 172
  29. 718
  30. 174
  31. 1084
  32. 969
  33. 871
  34. 527
  35. 667
  36. 278
  37. 1273
  38. 890
  39. 378
  40. 470

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