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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 572 · 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. 1.444 − 321 =
  2. 2.136 + 643 =
  3. 3.540 − 301 =
  4. 4.480 + 541 =
  5. 5.586 − 215 =
  6. 6.695 − 334 =
  7. 7.442 + 355 =
  8. 8.514 − 236 =
  9. 9.204 + 304 =
  10. 10.837 − 549 =
  11. 11.507 − 407 =
  12. 12.245 + 381 =
  13. 13.645 + 228 =
  14. 14.291 + 677 =
  15. 15.640 + 155 =
  16. 16.504 + 347 =
  17. 17.931 − 302 =
  18. 18.230 + 433 =
  19. 19.558 + 214 =
  20. 20.811 − 257 =
  21. 21.542 − 368 =
  22. 22.415 − 261 =
  23. 23.516 + 166 =
  24. 24.321 + 392 =
  25. 25.602 − 205 =
  26. 26.592 + 263 =
  27. 27.626 + 156 =
  28. 28.529 − 167 =
  29. 29.377 + 362 =
  30. 30.322 + 127 =
  31. 31.554 − 381 =
  32. 32.746 − 357 =
  33. 33.757 + 471 =
  34. 34.432 − 244 =
  35. 35.631 + 554 =
  36. 36.753 + 333 =
  37. 37.916 − 146 =
  38. 38.384 + 335 =
  39. 39.786 − 121 =
  40. 40.389 + 131 =

Answer key

  1. 123
  2. 779
  3. 239
  4. 1021
  5. 371
  6. 361
  7. 797
  8. 278
  9. 508
  10. 288
  11. 100
  12. 626
  13. 873
  14. 968
  15. 795
  16. 851
  17. 629
  18. 663
  19. 772
  20. 554
  21. 174
  22. 154
  23. 682
  24. 713
  25. 397
  26. 855
  27. 782
  28. 362
  29. 739
  30. 449
  31. 173
  32. 389
  33. 1228
  34. 188
  35. 1185
  36. 1086
  37. 770
  38. 719
  39. 665
  40. 520

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