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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 156 · 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. 1.274 + 475 =
  2. 2.212 + 208 =
  3. 3.605 + 419 =
  4. 4.819 − 183 =
  5. 5.289 + 191 =
  6. 6.619 + 518 =
  7. 7.407 + 496 =
  8. 8.136 + 146 =
  9. 9.964 − 321 =
  10. 10.459 − 252 =
  11. 11.834 − 633 =
  12. 12.747 + 119 =
  13. 13.864 − 519 =
  14. 14.288 + 464 =
  15. 15.417 − 118 =
  16. 16.914 − 126 =
  17. 17.572 + 336 =
  18. 18.245 + 683 =
  19. 19.615 − 355 =
  20. 20.916 − 723 =
  21. 21.955 − 801 =
  22. 22.455 + 211 =
  23. 23.893 − 644 =
  24. 24.578 + 227 =
  25. 25.217 + 296 =
  26. 26.769 + 115 =
  27. 27.157 + 299 =
  28. 28.393 + 403 =
  29. 29.667 − 272 =
  30. 30.223 + 608 =
  31. 31.879 − 517 =
  32. 32.148 + 458 =
  33. 33.261 + 665 =
  34. 34.342 + 171 =
  35. 35.678 + 244 =
  36. 36.658 − 289 =
  37. 37.191 + 349 =
  38. 38.846 − 502 =
  39. 39.517 − 216 =
  40. 40.916 − 406 =

Answer key

  1. 749
  2. 420
  3. 1024
  4. 636
  5. 480
  6. 1137
  7. 903
  8. 282
  9. 643
  10. 207
  11. 201
  12. 866
  13. 345
  14. 752
  15. 299
  16. 788
  17. 908
  18. 928
  19. 260
  20. 193
  21. 154
  22. 666
  23. 249
  24. 805
  25. 513
  26. 884
  27. 456
  28. 796
  29. 395
  30. 831
  31. 362
  32. 606
  33. 926
  34. 513
  35. 922
  36. 369
  37. 540
  38. 344
  39. 301
  40. 510

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