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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 346 · 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. 1.658 + 331 =
  2. 2.197 + 683 =
  3. 3.938 − 151 =
  4. 4.447 − 171 =
  5. 5.470 + 231 =
  6. 6.805 − 331 =
  7. 7.437 + 269 =
  8. 8.528 + 271 =
  9. 9.208 + 671 =
  10. 10.186 + 637 =
  11. 11.772 + 141 =
  12. 12.607 − 144 =
  13. 13.778 + 444 =
  14. 14.900 − 341 =
  15. 15.468 − 161 =
  16. 16.569 − 205 =
  17. 17.908 − 366 =
  18. 18.466 + 223 =
  19. 19.477 − 232 =
  20. 20.310 + 617 =
  21. 21.241 + 121 =
  22. 22.948 − 831 =
  23. 23.564 + 621 =
  24. 24.747 + 639 =
  25. 25.689 + 581 =
  26. 26.143 + 319 =
  27. 27.659 + 281 =
  28. 28.514 + 329 =
  29. 29.408 + 656 =
  30. 30.618 + 403 =
  31. 31.790 − 591 =
  32. 32.605 + 623 =
  33. 33.413 + 683 =
  34. 34.688 + 547 =
  35. 35.729 + 442 =
  36. 36.431 + 255 =
  37. 37.858 − 227 =
  38. 38.144 + 432 =
  39. 39.755 + 511 =
  40. 40.817 − 594 =

Answer key

  1. 989
  2. 880
  3. 787
  4. 276
  5. 701
  6. 474
  7. 706
  8. 799
  9. 879
  10. 823
  11. 913
  12. 463
  13. 1222
  14. 559
  15. 307
  16. 364
  17. 542
  18. 689
  19. 245
  20. 927
  21. 362
  22. 117
  23. 1185
  24. 1386
  25. 1270
  26. 462
  27. 940
  28. 843
  29. 1064
  30. 1021
  31. 199
  32. 1228
  33. 1096
  34. 1235
  35. 1171
  36. 686
  37. 631
  38. 576
  39. 1266
  40. 223

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