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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 670 · 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. 1.442 + 145 =
  2. 2.352 + 263 =
  3. 3.879 − 568 =
  4. 4.611 − 297 =
  5. 5.936 − 704 =
  6. 6.204 + 173 =
  7. 7.167 + 292 =
  8. 8.704 − 297 =
  9. 9.558 − 239 =
  10. 10.667 + 602 =
  11. 11.175 + 204 =
  12. 12.304 + 481 =
  13. 13.452 − 253 =
  14. 14.652 − 228 =
  15. 15.670 + 385 =
  16. 16.847 − 432 =
  17. 17.832 − 678 =
  18. 18.276 + 286 =
  19. 19.267 + 329 =
  20. 20.980 − 131 =
  21. 21.731 + 158 =
  22. 22.170 + 155 =
  23. 23.560 + 539 =
  24. 24.791 − 158 =
  25. 25.591 + 214 =
  26. 26.726 + 213 =
  27. 27.775 − 125 =
  28. 28.625 + 421 =
  29. 29.267 + 394 =
  30. 30.330 + 203 =
  31. 31.523 + 424 =
  32. 32.532 − 258 =
  33. 33.417 − 297 =
  34. 34.343 + 285 =
  35. 35.518 + 668 =
  36. 36.443 + 387 =
  37. 37.391 + 362 =
  38. 38.427 − 229 =
  39. 39.772 + 231 =
  40. 40.675 − 168 =

Answer key

  1. 587
  2. 615
  3. 311
  4. 314
  5. 232
  6. 377
  7. 459
  8. 407
  9. 319
  10. 1269
  11. 379
  12. 785
  13. 199
  14. 424
  15. 1055
  16. 415
  17. 154
  18. 562
  19. 596
  20. 849
  21. 889
  22. 325
  23. 1099
  24. 633
  25. 805
  26. 939
  27. 650
  28. 1046
  29. 661
  30. 533
  31. 947
  32. 274
  33. 120
  34. 628
  35. 1186
  36. 830
  37. 753
  38. 198
  39. 1003
  40. 507

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