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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 339 · 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. 1.238 + 263 =
  2. 2.776 + 398 =
  3. 3.761 + 407 =
  4. 4.638 + 345 =
  5. 5.186 + 631 =
  6. 6.672 − 547 =
  7. 7.597 + 595 =
  8. 8.526 − 381 =
  9. 9.471 + 616 =
  10. 10.484 − 321 =
  11. 11.183 + 601 =
  12. 12.507 + 221 =
  13. 13.508 − 244 =
  14. 14.935 − 581 =
  15. 15.507 + 422 =
  16. 16.629 + 591 =
  17. 17.452 + 201 =
  18. 18.198 + 443 =
  19. 19.503 + 229 =
  20. 20.646 − 465 =
  21. 21.501 + 521 =
  22. 22.841 − 549 =
  23. 23.495 − 154 =
  24. 24.503 − 308 =
  25. 25.518 − 279 =
  26. 26.290 + 264 =
  27. 27.256 + 365 =
  28. 28.952 − 531 =
  29. 29.180 + 121 =
  30. 30.180 + 645 =
  31. 31.721 + 261 =
  32. 32.283 + 497 =
  33. 33.256 + 667 =
  34. 34.672 + 259 =
  35. 35.195 + 178 =
  36. 36.468 − 158 =
  37. 37.187 + 395 =
  38. 38.863 − 118 =
  39. 39.260 + 496 =
  40. 40.480 + 313 =

Answer key

  1. 501
  2. 1174
  3. 1168
  4. 983
  5. 817
  6. 125
  7. 1192
  8. 145
  9. 1087
  10. 163
  11. 784
  12. 728
  13. 264
  14. 354
  15. 929
  16. 1220
  17. 653
  18. 641
  19. 732
  20. 181
  21. 1022
  22. 292
  23. 341
  24. 195
  25. 239
  26. 554
  27. 621
  28. 421
  29. 301
  30. 825
  31. 982
  32. 780
  33. 923
  34. 931
  35. 373
  36. 310
  37. 582
  38. 745
  39. 756
  40. 793

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