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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 805 · 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. 1.125 + 469 =
  2. 2.134 + 675 =
  3. 3.588 + 303 =
  4. 4.892 − 583 =
  5. 5.836 − 711 =
  6. 6.493 + 635 =
  7. 7.656 − 165 =
  8. 8.609 − 314 =
  9. 9.822 − 689 =
  10. 10.309 + 208 =
  11. 11.973 − 156 =
  12. 12.445 − 171 =
  13. 13.236 + 328 =
  14. 14.590 + 586 =
  15. 15.521 − 159 =
  16. 16.968 − 255 =
  17. 17.525 − 361 =
  18. 18.445 − 145 =
  19. 19.764 − 375 =
  20. 20.417 + 683 =
  21. 21.263 + 677 =
  22. 22.487 − 151 =
  23. 23.496 + 512 =
  24. 24.463 + 445 =
  25. 25.512 + 395 =
  26. 26.621 + 121 =
  27. 27.931 − 558 =
  28. 28.364 + 386 =
  29. 29.493 − 124 =
  30. 30.455 + 188 =
  31. 31.638 − 347 =
  32. 32.806 − 115 =
  33. 33.746 + 687 =
  34. 34.258 + 311 =
  35. 35.358 + 178 =
  36. 36.425 − 118 =
  37. 37.545 − 161 =
  38. 38.985 − 405 =
  39. 39.625 + 247 =
  40. 40.248 + 257 =

Answer key

  1. 594
  2. 809
  3. 891
  4. 309
  5. 125
  6. 1128
  7. 491
  8. 295
  9. 133
  10. 517
  11. 817
  12. 274
  13. 564
  14. 1176
  15. 362
  16. 713
  17. 164
  18. 300
  19. 389
  20. 1100
  21. 940
  22. 336
  23. 1008
  24. 908
  25. 907
  26. 742
  27. 373
  28. 750
  29. 369
  30. 643
  31. 291
  32. 691
  33. 1433
  34. 569
  35. 536
  36. 307
  37. 384
  38. 580
  39. 872
  40. 505

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